Ever since 1952, when a Republican senator, Arthur H. Vandenberg, coined the phrase, it has been said that in American foreign affairs, politics should stop at the water’s edge. Now, with President Bush confronting an opposition party in control of Congress, that fiction is becoming harder to maintain.

With a final stop in Lisbon on Friday, House Speaker Nancy Pelosi headed home to a Washington that is still ringing with complaints from senior Bush officials that her stop in Damascus to visit with Bashar al-Assad, the Syrian president, bolstered the image of Syria at a time when United States policy is to isolate it.

The tone of the complaints — particularly Vice President Dick Cheney’s public characterization of her visit as “bad behavior” — contrasts sharply with the administration’s silence about a similar trip to Damascus a week ago by Republican lawmakers, Representatives Frank R. Wolf of Virginia, Joe Pitts of Pennsylvania and Robert B. Aderholt of Alabama.

Nor was there much heard from the White House about a meeting that Representative Darrell Issa, a California Republican, had with Mr. Assad on Thursday, a day after Ms. Pelosi met with the Syrian president.

Ms. Pelosi, in a telephone interview from Lisbon on Friday, said she could not account for the Bush administration’s assault, which she at one point equated to a tantrum. (She said her children were teasing her about Mr. Cheney’s accusation of bad behavior.) Defending her trip, Ms. Pelosi said that members of Congress had a responsibility to play a role in national security issues and that they needed to be able to gather information on their own, and not be dependent on the White House.

“I am used to the administration; nothing surprises me,” she said. “Having said that, I hope we can have the opportunity to convey to the president what we saw.”

Ms. Pelosi, as House speaker, outranks her other touring Congressional colleagues, and is the highest-ranking United States official to visit Damascus in years. Still, the criticism from Bush officials was sharp, particularly about Ms. Pelosi's delivery of a message to Mr. Assad that Israel was ready for peace talks. The office of the Israeli prime minister, Ehud Olmert, later issued a statement saying that such talks could take place only if Syria stopped assisting terrorist groups.

“Don’t you get enraged when this kind of thing happens?” Rush Limbaugh asked Mr. Cheney during a radio interview on Thursday.

“I think it is, in fact, bad behavior on her part,” the vice president replied. “She doesn’t represent the administration. The president is the one who conducts foreign policy, not the speaker of the House.”

Democrats say the complaints have a certain political expediency to them, and note that many of the same people criticizing Ms. Pelosi’s decision to delve into foreign policy were fine when Newt Gingrich, then the Republican speaker of the House, made his own foray into foreign policy back in 1997.

The Republican House leader, John A. Boehner of Ohio, criticized Ms. Pelosi’s trip, telling reporters that she was in Syria “for one reason, and that is to embarrass the president.” In 1997, Mr. Boehner accompanied Mr. Gingrich to China, and called the trip “very educational.”

Ms. Pelosi, during the telephone interview, spoke at length about the value of the trip, the ecumenical makeup of the her delegation, the seriousness of their conversations with Middle Eastern leaders and the fact that most members of the delegation were steeped in these foreign policy issues. Ms. Pelosi also spoke of the Democrats’ determination to hold to the Bush administration line on issues they discussed.

Among those on the trip were two other California Democrats, Representatives Tom Lantos, a Holocaust survivor, and Henry A. Waxman, an advocate of Israel; as well as Representative Keith Ellison of Minnesota, a Democrat who is the first Muslim elected to Congress. During the interview, Ms. Pelosi said that while Congress was breaking with the president on Iraq, there was no distance between her delegation and the White House on support for Israel and on the need for Syria to stop supporting terrorist groups and allowing infiltration into Iraq.

“We understand our responsibilities when we leave the country,” Ms. Pelosi said. “On all the issues, it was a very direct message, very consistent with the Bush administration’s message.” She said her message “was not always the one everyone wanted to hear.”

“I come back thinking, all right, we will get through their tantrum,” Ms. Pelosi said, in a reference to the administration, “but the fact is, we accomplished what we set out to do. I think we improved the understanding among the different parties.”

In Syria, she said Mr. Waxman made a case-by-case appeal to Mr. Assad on the behalf of Syrian dissidents. She said they met for more than an hour with Mr. Assad and more than three hours with King Abdullah of Saudi Arabia.

Edward P. Djerejian, the former American ambassador to Israel and Syria who helped draft the Iraq Study Group report that recommended that the United States open a diplomatic initiative towards Syria, noted that Ms. Pelosi’s visit, in many ways, followed the recommendations of the bipartisan group.

But, he added, Senator Vandenberg’s 1952 adage about politics stopping at the water’s edge “was probably a high point,” in bipartisan support for foreign policy.