Watch Wolf Blitzer's exclusive reports from Pyongyang, North Korea, for the latest on rising tensions between North and South Korea. Don't miss "The Situation Room" today at 5 p.m. ET on CNN.
Seoul, South Korea (CNN) -- North Korea did not retaliate as threatened Monday after a South Korean military exercise that it had warned could lead to war.
At the same time, the North agreed to allow U.N. monitors access to its uranium-enrichment facility and take other steps that could defuse tension if implemented, including considering the formation of a military commission made up of representatives from the North, the South and the United States.
Those steps generated at least the possibility of rare optimism on the Korean peninsula, which has been gripped by anxiety since the sinking of a South Korean warship killed 46 sailors in March. Tensions rose higher last month, when North Korea shelled a South Korean island, killing four people.
The latest developments came amid a visit to North Korea by Bill Richardson, the former U.S. ambassador to the United Nations and current governor of New Mexico.
"Maybe we had a little impact with them," he said Monday of the North Korean leaders.
In advance of South Korea's live-fire naval drill, North Korea had warned that the action could ignite a war and threatened to respond militarily.
The exercise ended peacefully, however, after an hour and 34 minutes. North Korean military leaders said retaliation wasn't necessary but issued a stern warning to South Korea and the United States, according to the state-run Korean Central News Agency.
Yet Richardson said the North also has agreed to allow monitors from the International Atomic Energy Agency access to the nation's uranium-enrichment facility and to negotiate a deal for a third party, such as South Korea, to buy fresh-fuel rods from North Korea.
In addition, North Korean leaders said they would discuss the formation of a military commission consisting of representatives from North Korea, South Korea and the United States to monitor and prevent conflicts in the disputed areas of the West Sea.
The fact that Pyongyang agreed to consider engaging in a multilateral dialogue with other nations through the commission is significant, said Han Park, a professor at the University of Georgia's School of Public and International Affairs and director of the university's Globis Center for the Study of Global Issues.
Dialogue between the North and South alone is "less desirable, because the two are very highly emotionally charged. It's like a family feud, if you will," said Park, a frequent visitor to North Korea who has close, regular contact with high-ranking North Korean officials. That's why the addition of other nations -- the United States and possibly even China -- is necessary, he said.
Such a commission would be likely to discuss one of the most pressing issues, the boundary in territorial waters, he said: "I think that will continue to be a source of problems." Topics like North Korea's nuclear program also could be discussed, he said.
The United States' political will to deal directly with North Korea is also important, he said: "The U.S. should not be a hostage of South Korean politics or policy."
There also was talk about creating a hot line between the two nation's militaries "to avert potential crises," according to a statement from Richardson. But Park noted that hot lines have previously been in place, and when tensions escalate, both sides will cut off the line.
Richardson and others emphasized to North Korean leaders that failing to retaliate after the exercise would cast them in a positive light, he said.
"I am encouraged by the news that North Korea will not react militarily to South Korea's drills," Richardson said in the statement. "During my meetings in Pyongyang, I repeatedly pressed North Korea not to retaliate.
"The result is that South Korea was able to flex its muscles, and North Korea reacted in a statesmanlike manner. I hope this will signal a new chapter and a round of dialogue to lessen tension on the Korean peninsula."
Park said he believes that the lack of retaliation by North Korea, while "a welcome sign," is a strategic move aimed at good public relations.
"They were taking the high road, so to speak," he said. "I think they're trying to win the hearts and minds of the people in South Korea as well as around the world." Public relations is "very high on North Korea's agenda," he added.
The U.S. State Department welcomed the North's muted response.
"This is the way countries are supposed to act," U.S. State Department spokesman P.J. Crowley said. "The South Korean exercise was defensive in nature. The North Koreans were notified in advance. There was no basis for a belligerent response."
Asked whether North Korea could be waiting for its southern neighbor to drop its guard before retaliating, Richardson acknowledged to CNN that is possible but said he thinks the fact that Pyongyang "took responsible action" shows they are moving into a new chapter.
"I think they deserve credit for holding back," he said. "I think North Korea may be sending a signal that they're ready to re-engage after having behaved very negatively."
Richardson is wrapping up a five-day unofficial trip to North Korea, accompanied by CNN's Wolf Blitzer. After fog delayed his departure Monday, the governor was set to leave Pyongyong around 7 a.m. Tuesday (5 p.m. ET Monday) for Beijing, before returning to the United States.
The South Korean military remained on high alert after the drill ended and is observing the North carefully, the country's Joint Chiefs of Staff said. During the drill, fighter jets took to the sky in preparation for possible North Korean retaliation, according to the South Korean defense ministry.
The drill -- and the possibility of a North Korean military response -- prompted such concern in the United States that Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, came into the Pentagon on Sunday night to monitor the drill directly, two Pentagon officials said.
The United States maintained a contingency communications plan throughout the night, so the U.S. and South Korean military were in constant contact, the officials said. The United States had satellites and other reconnaissance assets overhead watching for North Korean troop or weapons movements but did not deploy aircraft carriers or fighter jets, the officials said.
The U.S. military wanted to keep a low profile so as not to send any mistaken signals to North Korea, officials said.
Mullen and his aides were in the secure National Military Command Center inside the Pentagon from 10 p.m. to midnight Sunday, a senior U.S. military official said. He was constantly in contact via telephone with Adm. Robert Willard, commander of the U.S. Pacific Command in Hawaii, and Gen. Walter Sharp, commander of U.S. forces in South Korea, the official said.
The United States established a crisis team last week to monitor events on the Korean peninsula, the official said. For now, it remains on watch. America has about 25,000 troops in South Korea.
The South Korean president's office defended the drill, saying, "In a divided country that is militarily pitted against each other, it is natural that as a sovereign country, we will conduct military exercises and defend our territory."
The military exercise took place in waters just south of Yeonpyeong Island, where a North Korean shelling on November 23 killed two South Korean marines and two civilians.
The North has accused the South of provoking the attack because shells from a South Korean military drill landed in the North's waters.
"The revolutionary armed forces of the DPRK (Democratic People's Republic of Korea) did not feel any need to retaliate against every despicable military provocation like one taking revenge after facing a blow," KCNA reported North Korean military officials as saying Monday. "The second and third powerful retaliatory strike to be made by the revolutionary armed forces of the DPRK knowing no limit as declared before the world will lead to blowing up the bases of the U.S. and South Korean puppet warmongers."
North Korean military officials also said the United States and South Korea perpetuated military provocation, "far from drawing a lesson from the disgraceful defeat they suffered" from the last Yeonpyeong shelling, according to KCNA.
About 8,000 residents were ordered to take cover in Yeonpyeong, Baengnyeong, Daecheong, Socheong and Udo in the hours leading up to the drill.
But after the drill ended Monday, South Korea's Joint Chiefs of Staff said the emergency order for civilians on five islands to "take cover" had been lifted.
South Korea has not said whether any additional naval drills are imminent.
In South Korea, "this was an extraordinarily tense day," CNN's Kyung Lah said. "You had civilians hiding in bunkers."
The U.N. Security Council wrangled for nearly eight hours Sunday over growing tensions in the Korean peninsula before ending its emergency meeting without a unified statement.
Susan Rice, U.S. ambassador to the United Nations, said Monday that the United States would have liked a statement condemning North Korea's shelling of Yeonpyeong Island and urging restraint. Although it was unfortunate that members did not agree on such a statement, she said, "I think most council members concluded that the window of relevance, or principal relevance, for the statement we were discussing yesterday has largely passed."
Meanwhile, China asked the two Koreas to exercise "maximum restraint." China's deputy permanent representative to the United Nations, Wang Min, made the statement during the Security Council meeting.
In his statement, Wang reiterated China's call for both sides to return to the negotiating table.
China is the isolated North's sole major ally and provides it with a crucial fuel and food lifeline.
CNN's Kyung Lah and Jiyeon Lee in Seoul; Richard Roth and Whitney Hurst at the United Nations; Barbara Starr in Washington; and Ashley Hayes in Atlanta contributed to this report.