Three Republican members of the U.S. Congress made a quick trip Sunday into opposition-held northwest Syria in the first known visit to the war-torn country by American lawmakers in six years. They urged the Biden administration and regional partners to keep up the pressure on Syrian President Bashar Assad.

The roughly one-hour stop was a signal of the significant support on Capitol Hill for the opposition in Syria's long civil war.

U.S. Rep. French Hill of Arkansas, one of the three lawmakers, told The Associated Press by telephone after leaving Syria that the trip was the latest of his several to the region this summer to press the U.S. government and Arab allies to continue pushing for a political resolution to the war.

Hill said his message was in behalf of “those in Syria who want to have their own representative government."

The conflict began in 2011 after Assad launched a campaign to crush what began as a peaceful uprising against his family's autocratic rule. Assad has held on to power despite the uprising thanks in large part to the armed intervention by allies Russia and Iran. But the conflict has splintered the country, killed at least 300,000 civilians, and displaced half of Syria's prewar population of 23 million.

The trip comes at a time that Middle East leaders have begun restoring relations with Assad's government. By doing so, the Arab leaders are breaking sharply from the U.S., which is pushing to keep Assad isolated over government abuses that the United Nations says include repeated use of chemical weapons against Syrian civilians.

The U.N says 300,000 Syrian civilians died in the first 10 years of the conflict.

Hill and his fellow lawmakers, Ben Cline of Virginia and Scott Fitzgerald of Wisconsin, entered Syria early Sunday from Turkey via the Bab al-Salama crossing in northern Aleppo province.

They were greeted by orphans who attend Wisdom House, a school for orphans that is a project of the Syrian Emergency Task Force, a U.S.-based Syrian opposition organization that facilitated the lawmakers’ trip.

Hill’s constituents in Arkansas have been leading donors to the school. “It was an emotional day for me to see those children, holding up pictures of their parents who’d been murdered by Assad's regime, getting a hug and a kiss from them," he said.

The children were students at Wisdom House, a school for orphans that is a project of the Syrian Emergency Task Force, a U.S.-based Syrian opposition organization that facilitated the lawmakers’ trip. Hill's constituents in Arkansas have been leading donors to the school.

The lawmakers met with opposition and humanitarian leaders, including Raed Saleh, head of the White Helmets, a volunteer group of first responders known for extracting civilians from buildings flattened by bombing.

Saleh spoke with the lawmakers about the political status of the conflict in Syria and on continuing humanitarian efforts for victims of a earthquake earlier this year in Turkey and Syria, the White Helmets said on X, the site formerly known as Twitter.

Security concerns meant there was no public announcement of the trip beforehand. Hill spoke from neighboring Turkey, where the congressmen also held a series of meetings.

The last-known trip by a U.S. lawmaker to Syria was in 2017, when Sen. John McCain, R-Ariz., visited U.S. forces stationed in northeast Syria’s Kurdish region. McCain had previously visited Syria and met with armed opposition fighters.

Also in 2017, U.S. Rep. Tulsi Gabbard, D-Hawaii, visited Damascus, the capital, and met with Assad, a decision that was widely criticized at the time.

Since the beginning of the uprising-turned-civil-war in Syria, the U.S. government has backed the opposition and has imposed sanctions on Assad’s government and associates over human rights concerns. Washington has conditioned restoring relations with Damascus on progress toward a political solution to the 12-year conflict.

A growing number of Arab leaders are moving to end their own isolation of Assad, in line with arguments that engagement is the best way to address the flow of refugees, illegal drugs and other problems for the region from Syria. The 22-member Arab League recently reinstated Syria as a member after cutting ties earlier in the Syrian war.

Hill said he had engaged Middle East governments repeatedly over the past three months about “what are the ramifications of the Arab League’s admission of Syria back to the League and yet asking nothing” of Assad in return in terms of greater political freedoms and an end to rights abuses.

Hill also is pushing for the U.S. and Arab countries to press Assad harder on Syria's status as the world's leading global trafficker of Captagon, a highly addictive amphetamine.

Congress late last year passed a mandate for the U.S. to target Captagon smuggling in the Middle East, and President Joe Biden signed it into law.

Hill accused Biden of not doing enough to pressure Assad to adopt political reforms and stop the flow of that illegal drug, an important source of revenue for the Assad government.

"What I believe Syria needs, and the same thing the U.S. needs, is American leadership, Hill said.

Neither the State Department nor the White House had immediate comment on the Republican lawmakers' trip.

Control of northwest Syria is largely split between the Turkish-backed opposition groups and Hayat Tahrir al-Sham, a group that was originally founded as an offshoot of al-Qaida and is designated as a terrorist organization by the United States. In recent years, the group’s leadership have attempted to publicly distance themselves from their al-Qaida origins.

The Turkish-backed opposition groups have regularly clashed with Kurdish forces based in northeast Syria, who are allies of the United States in the fight against the Islamic State.