Story highlights

North Korea last week announced a freeze on nuclear and missile tests

In return, the Unites States has agreed to resume providing food aid

Talks this week were aimed at setting the details of the food assistance

The U.S. envoy says it's not yet clear when the shipments will begin

(CNN) —  

A U.S. envoy expressed optimism that food aid would find its way to those in need in North Korea after two days of talks with officials from Pyongyang, but it remained unclear when the shipments might begin.

Robert King, the U.S. special envoy for North Korean human rights issues, met with North Korean representatives in Beijing to thrash out the details of a plan to allow the resumption of food aid to the North.

“We resolved the administrative issues that we were concerned with,” King said Thursday before leaving for Washington to report the results of the discussions. He described the meetings as “very productive, positive talks.”

He added, though, that the timing of the food deliveries was not yet clear. “We’re still working on the details,” he said. “Not all of those questions have been worked out.”

North Korea last week announced an agreement to freeze its nuclear and missile tests, along with uranium enrichment programs, and allow the return of U.N. nuclear inspectors. The United States said it would provide 240,000 metric tons of nutritional assistance to the impoverished country.

The United States had suspended shipments of food aid to North Korea in 2009 amid tensions over Pyongyang’s nuclear program and concerns that the supplies were not reaching those most in need.

The initial deal last week to resume the deliveries came after the the two countries revived negotiations that had stalled after the death in December of the longtime North Korean leader Kim Jong Il.

The talks this week were held in order to finalize points like what ports will be used to dock incoming ships, how the distribution of the food will be monitored and which nongovernmental organizations will be involved.

The agreement last week was cautiously welcomed by U.S. officials in the hope that a new era in relations with the North would begin and lead to a resumption of multilateral talks aimed at the denuclearization of the Korean peninsula.

But Pyongyang has stepped up its rhetoric against the South Korean president, Lee Myung-bak, and his government since Kim Jong Un took over from his father, Kim Jong Il, as North Korean leader.

Earlier this week, North Korean television aired footage of a military unit carrying out live-fire drills in sight of a South Korean island.

It showed tanks repositioning and an artillery machine being prepared, overlooking waters that have seen a number of violent incidents over the years. North Korea shelled Yeonpyeong Island in November 2010, killing four South Koreans, claiming it was responding to a South Korean military drill in the area.

Li Gum-chol, a North Korean deputy commander, said: “We will turn Seoul into a sea of flames by our strong and cruel artillery firepower, which cannot be compared to our artillery shelling on Yeonpyeong Island. We are training hard, concentrating on revenge to shock Lee Myung-bak’s traitorous group and the military warmongers in South Korea.”

The United States and South Korea are carrying out annual joint military drills, which North Korea has condemned as a provocation. Now, Pyongyang is staging its own.

CNN’s Chi-Chi Zhang and Jethro Mullen contributed to this report.