KABUL, Afghanistan (CNN) -- Sen. Barack Obama said Sunday that United States needs to focus on Afghanistan in its battle against terrorism.
Sen. Barack Obama and Afghan President Hamid Karzai meet Sunday in Kabul.
"The Afghan government needs to do more. But we have to understand that the situation is precarious and urgent here in Afghanistan. And I believe this has to be our central focus, the central front, on our battle against terrorism," Obama said Sunday on CBS' "Face the Nation."
"I think one of the biggest mistakes we've made strategically after 9/11 was to fail to finish the job here, focus our attention here. We got distracted by Iraq," he said.
Obama said troop levels must increase in Afghanistan.
"For at least a year now, I have called for two additional brigades, perhaps three," he told CBS. "I think it's very important that we unify command more effectively to coordinate our military activities. But military alone is not going to be enough."
Obama met Sunday with Afghan President Hamid Karzai, a leader the Democratic senator has criticized for not doing enough to rebuild the war-torn nation.
The presumptive Democratic presidential nominee met with Karzai in Kabul, the capital city, during Obama's first visit to the Asian nation.
Karzai's spokesman characterized the senator's message as pleasant.
"They're happy to be in Afghanistan. They reassured the support of U.S. people to Afghanistan," Humayoon Hamidzada said.
Karzai met with the congressional delegation that includes Obama, and they discussed the achievements of the Afghan government as well as challenges such as terrorism, corruption and illegal drugs. See a map with photos of Obama's trip »
McCain's senior foreign policy adviser criticized Obama on Sunday for "stubbornly adhering to an unconditional withdrawal that places politics above the advice of our military commanders, the success of our troops and the security of the American people."
"Barack Obama is wrong to advocate withdrawal at any cost just as he was wrong to oppose the surge that has put victory within reach. It is a strategy for defeat, and it is the only strategy Barack Obama has ever supported," Randy Scheunemann said in a statement.
Obama traveled to eastern Afghanistan on Saturday to visit American forces under NATO's Regional Command East, the coalition's Combined Joint Task Force said. Obama is joined by Sen. Charles Hagel, a Republican from Nebraska, and Sen. Jack Reed, a Democrat from Rhode Island.
In a joint statement released Sunday, the three senators expressed confidence that progress would be made in Afghanistan.
"We need a sense of urgency and determination. We need urgency because the threat from the Taliban and al Qaeda is growing and we must act; we need determination because it will take time to prevail. But with the right strategy and the resources to back it up, we will get the job done," they said in the statement.
Shortly after meeting with Karzai, Obama left Afghanistan to continue a trip that will take him to the Middle East and Europe.
Obama will travel to Jordan, then visit Israel, Germany, France and England.
Although Obama is making the trip as a senator from Illinois and not a presidential candidate, it is aimed at boosting Obama's foreign policy credentials. Watch analyst discuss Obama's visit in Afghanistan »
Obama has made Afghanistan a key focus of his foreign policy, saying he would make it the central front in the "war on terror" if elected.
Earlier in the day, Obama dined with U.S. troops at an American base in the Afghan capital. Watch Obama get some "chow" »
"This is my favorite thing to do," Obama said as he sat with about two dozen soldiers, sailors and airmen in a military mess hall.
Ahead of the trip to Afghanistan, Obama, Reed and Hagel stopped in Kuwait to visit U.S. troops, Obama campaign spokesman Robert Gibbs said. They left Washington on Thursday.
In Kuwait, the senators visited Camp Arifjan for about two hours to meet with U.S. Army Central leadership, take a brief tour of the base and talk with soldiers, U.S. military spokesman Lt. Col. Bill Nutter said.
The senators also met with about 1,000 military members at a gymnasium, who cheered jubilantly at their arrival. Later, Obama played basketball with some soldiers, drawing cheers from his successful shots. Watch Obama visit troops in Kuwait »
Asked whether he would have tough talk for the leaders of Afghanistan and Iraq, Obama said he was "more interested in listening than doing a lot of talking."
"I think it is very important to recognize that I'm going over there as a U.S. senator. We have one president at a time, so it's the president's job to deliver those messages," Obama said.
The fight in Afghanistan has become a more pressing issue on the political radar. Three times as many coalition soldiers and other military personnel have died in July in Afghanistan, compared with Iraq. July's death toll for coalition troops reached 22 after the Friday death of a Canadian soldier was announced.
Nine U.S. soldiers were killed July 13 in a fight with about 200 Taliban militants in eastern Afghanistan. It was the deadliest attack on U.S. troops in Afghanistan in three years.
CNN's Wahidullah Mayar contributed to this report.