Ms. Pelosi, the third-highest ranking elected official in the United States government behind the president and vice president, is the most senior American leader to visit the country since Syrian-American relations faltered in 2003.

The United States has been trying to isolate Syria diplomatically, accusing the country of allowing militant fighters safe passage into neighboring Iraq and of meddling in Lebanese politics. The government in Damascus denies the accusations. Ms. Pelosi, who is leading a group of Congressional representatives visiting the country, was greeted at Damascus airport this afternoon by Walid al-Moallem, the Syrian Foreign Minister, who whisked her away for a tour of old Damascus. She made no public remarks.

The group of lawmakers is expected to meet with members of the Syrian parliament and opposition leaders over dinner this evening at the American ambassadorial residence in Damascus. The United States recalled its ambassador in 2005, following allegations that the Syrian regime may have had a hand in the assassination of the former Lebanese Prime Minister, Rafik Hariri.

President George W. Bush criticized Ms. Pelosi’s visit today during a news conference at the White House. He said the visit sent “mixed signals” that “lead the Assad government to believe they are part of the mainstream of the international community, when in fact they are a state sponsor of terror” and supporter of anti-Israeli militants like Hamas and Hezbollah. “Sending delegations hasn’t worked,” Mr. Bush said. “It’s just simply been counterproductive.”