A senior figure from a Syrian rebel group with links to al Qaida was allowed into the United States for a brief visit, raising questions about how much the Obama administration will compromise in the search for partners in the conflict.

Labib al Nahhas, foreign affairs director for the Islamist fighting group Ahrar al Sham, spent a few days in Washington in December, according to four people with direct knowledge of the trip and who spoke on condition of anonymity because of the sensitivity of U.S. relations with Syrian rebels.

His previously undisclosed visit is a delicate matter for both sides – the conservative Salafist insurgents risk their credibility with even perceived ties to the United States, and the U.S. government risks looking soft on screenings by allowing entry to a member of an Islamist paramilitary force.

National security analysts say U.S. authorities likely knew of Nahhas’ arrival – intelligence agencies for years have watched his group’s interactions with al Qaida’s Syrian branch, the Nusra Front.

That suggests that authorities granted him entry at a time when U.S. immigration authorities face political pressure to block visitors with even tenuous ties to extremist groups. Four months after Nahhas entered the United States on a European passport, U.S. authorities denied entry to a well-known Syrian humanitarian leader who had been approved to visit Washington to receive an award from international aid groups.

“They’re treating Labib al Nahhas as an individual, and it’s also useful to have someone to talk to on the other side,” said Faysal Itani, a Syria specialist with the Atlantic Council’s Rafik Hariri Center for the Middle East, who said he’d known about Nahhas’ visit. “They could make, quickly, the decision that he’s persona non grata in the United States and yet they haven’t.”

A Syrian opposition official with knowledge of the matter said it shouldn’t have been surprising that he was allowed entry because Ahrar al Sham is not among U.S.-designated terrorist groups. He said Nahhas hadn’t planned meetings with any U.S. officials but wanted to speak with “third parties” who might be able to influence policymakers. He declined to elaborate on the “third parties;” others said the plan was to meet with lobbyists and Middle East researchers.

The State Department declined to answer whether any U.S. officials knew in advance or expressed reservations about Nahhas’s presence in Washington, or whether State Department officials had assisted his entry.

“We don’t discuss visa records,” said State Department spokesman John Kirby. “In general, U.S. officials have engaged with a range of Syrian opposition groups, including Ahrar al Sham. … However, we are not going to get into the details of any such discussions.”

U.S. officials have long struggled with how to deal with Ahrar al Sham, one of the largest insurgent armies in Syria.

The group’s ultimate vision is Islamist rule for Syria and its old links to al Qaida are no secret: One of the group’s founders, Abu Khalid al Suri, was memorialized by al Qaida leader Ayman al Zawahiri after his death in a bombing.

By all accounts, Ahrar al Sham is much more ideologically diverse than al Qaida, encompassing members ranging from followers of a more moderate, Muslim Brotherhood-style Islamism to Salafist jihadists whose beliefs are virtually identical to al Qaida’s.

“They’re not al Qaida but they are Salafi jihadists – they’re just not transnational ones,” Itani said of Ahrar al Sham.

Ahrar continues to frustrate the United States and its allies with its operational coordination with al Qaida’s Nusra Front, including a joint attack this month in the Syrian village of Zara that resulted in what human rights group called the massacre of at least 19 civilians from the Alawite minority. An Ahrar official told McClatchy the operation was defensive and not sectarian in nature; he said fighters perceived foreign powers weren’t stopping regime advances in the area.

Even with circumstances of the killings in dispute, the participation of Ahrar al Sham in the operation – alongside al Qaida loyalists and while a truce was in effect – makes it all the more difficult for Nahhas to convince the world of his group’s commitment to working in the mainstream.

For months, Nahhas, serving as Ahrar’s ambassador to the outside world, has flown to foreign capitals and penned op-eds showing a willingness to work with the West, only to see his efforts undermined by the military wing of the group. Last summer, only a month after Nahhas pledged Ahrar’s commitment to a “moderate” future for Syria, the group issued a statement praising the late Taliban chief Mullah Omar as the embodiment of “the true meanings of jihad and sincerity.”

“The more moderate-sounding wing of Ahrar al Sham represented by Labib Nahhas does not seem to have a lot of influence over hardliners in the armed cadre,” said Aron Lund, who monitors the conflict as a nonresident associate at the Carnegie Endowment for International Peace and as editor of Syria in Crisis. “His initiatives keep getting slapped down by the leadership.”

The Obama administration has considered slapping a terrorist label on the group, and Secretary of State John Kerry has lumped Ahrar in the same category as blacklisted groups the Islamic State, Nusra Front and Hamas.

Officials so far have held back on a designation, privately saying that they’ve calculated it would do more harm than good on the ground.

Ahrar’s militiamen – estimates of its strength range from 7,000 to the 27,000 the group itself claims – are considered skilled, disciplined and well equipped. In several strategic locations, they are the force preventing a rout of the U.S.-backed rebels by Nusra Front or the Islamic State. They also have boosters in U.S.-friendly Qatar and Turkey, a NATO ally.

At the time of Nahhas’s visit to Washington, the Syrian opposition official said, Saudi Arabia was planning its Riyadh conference of rebel factions, and the groups wanted a chance to clear up Western misconceptions. The official said that Nahhas wasn’t just representing Ahrar al Sham, but was acting as an emissary for several rebel groups who wanted to deliver “an accurate picture of the military and political situation, since we always felt that fundamental parts of reality in Syria are missing in D.C.”

Among those tough realities, he said, is that rebel groups often have little choice but to work alongside Nusra – rejecting Nusra would mean picking a fight with one of the few reliable forces battling the regime.

“We are fighting the regime, Iranians, Hezbollah, YPG, Daesh and now the Russians,” the opposition official said, listing some of the many parties to the Syrian conflict. “We cannot keep opening fronts and adding enemies when our ‘allies’ are not supporting us.”

That idea lies at the heart of years of mutual frustration between Washington and Ahrar al Sham or other Syrian rebel groups that sometimes partner with the Nusra Front. U.S. officials are wary of the rebels because of ties to al Qaida, and the rebels say the U.S. record in Syria gives them no faith that they’d be protected if they broke from a group with battlefield influence.

Given the State Department’s growing impatience with Syrian insurgents’ “co-mingling” with Nusra Front, it’s unclear whether Nahhas would be welcomed back to Washington.

“Straddling the jihadi-mainstream divide has served them very well earlier in the conflict,” Lund said of Ahrar al Sham, “but by now their inability to come down on one side or the other is starting to look more like weakness.”