President Bush and President Hamid Karzai of Afganistan, close allies in fighting terrorism, found much to agree on as they completed a two-day meeting on Monday, but differs on the role of Iran in Afghanistan.

Mr. Karzai characterized Iran as a helper in a CNN interview broadcast. When the two men told reporters, Mr. Bush pointedly disagreed, he said, “I would be very cautious about whether the Iranian influence in Afghanistan is a positive force.”

Iran has sent workers to Afghanistan to provide help to villages, but American officials contend that Tehran is also providing weapons into the nation.

Mr. Bush viewed Iran as a state sponsor of terrorism, and is deeply suspicious of its nuclear ambitions.

Mr. Bush said, “The president knows best about what’s taking place in his country and of course, I’m willing to listen,” but from my perspective, the burden of proof is on the Iranian government to show us that they are a positive force.”

It was a rare moment of daylight between the American and Afghan leaders. President Bush has been trying to shore up Mr. Karzai facing lots of challenges, including a renascent Taliban, a prospering opium trade, government corruption and threat of Al Qaeda.

Qaeda network had reconstituted itself in the mountainous territory along the Afghanistan-Pakistan border, according to the recent conclusion of a national intelligence. Unsuccessful search for Al Qaeda operatives especially Osama bin Laden, has disappointed Mr. Bush. It has created tension between Mr. Karzai and Pakistani counterpart, Gen. Pervez Musharraf. Both leaders are expected to meet this week at jirga, an assembly of leaders from their nations.

Mr. Karzai said the session would focus on “how we can carry on the fight against terrorism in both countries.”

Meanwhile, Mr. Bush declined to answer directly when he was asked about his strategy for hunting down Qaeda leaders, he said, “I’m confident, with real actionable intelligence, we will get the job done.”