Pelosi spoke to journalists at the end of a two-day visit to Syria, which the White House criticised as undermining US efforts to isolate Syria.
Syria's official news agency quoted al-Assad as telling Pelosi: "Syria has adopted the Arab initiative. Its strategic choice is peace."
George Bush, the US president, has said Pelosi's trip signals that the al-Assad government is part of the international mainstream when it is not.
"A lot of people have gone to see President Assad ... and yet we haven't seen action. He hasn't responded," Bush said.
On Wednesday, a spokesman for the White House national security council called the visit "counterproductive".
Pelosi said she and other members of her congressional delegation told al-Assad their concerns about fighters crossing from Syria into Iraq.
The house speaker also said she had spoken to the president about Israeli soldiers captured by the Lebanese group Hezbollah and Palestinian groups.
Democrats have argued that the US should engage with its rivals in the region - Iran and Syria - to make headway in easing the problems in Iraq, Lebanon and the Israeli-Arab peace process.