WASHINGTON  — After playing a critical role in the prisoner swap that freed the last American soldier held captive in Afghanistan, Qatar faces new scrutiny by the United States over whether it will enforce restrictions on five released Taliban fighters.

Concerns have been expressed by U.S. intelligence officials and Congressional advisers over the role of the Gulf emirate as a bridge between Washington and the world of radical Islam. But the White House says it received “very specific” assurances from Qatar on the terms under which it agreed to accept and keep tabs on the five Afghans.

“I have little confidence in the security assurances regarding the movement and activities of the now released Taliban leaders and I have even less confidence in this administration’s willingness to ensure they are enforced,” said Mike Rogers, a republican Chairman of the House Intelligence Committee.

Sergeant Bowe Bergdahl, 28, was released on Saturday after being held for five years by the Taliban, in exchange for five detainees held at the U.S. military prison in Guantanamo Bay, Cuba. The men included former Taliban deputy defense minister Mohammad Fazl.

They face a year-long travel ban in Qatar, according to U.S. and Qatari officials.

Two U.S. officials said the State Department and U.S. intelligence agencies had expressed skepticism in the past about Qatar’s commitment to supervise militants released into their custody.

The State Department’s concerns about Qatar’s supervision of released militants were detailed in a diplomatic cable dated February 2009 by the U.S. embassy in Doha, Qatar’s capital, citing the case of Jarallah al-Marri, a former Guantanamo detainee released to Qatar in July 2008.

In the cable, the U.S. embassy criticized Qatar for failing to follow through on promises to bar al Marri from leaving Qatar, noting he made two trips to Britain since his release from Guantanamo, and that during his second visit, in early 2009, British authorities arrested him.