But the panel concluded that the drawdown nonetheless “undermines confidence in the American commitment to Syria.” It also notes that numerous Islamic State militants and their families remain detained in Syria, and that if their fate is unaddressed, they could in the long run boost the terrorist group’s resurgence.

The interim report, obtained Friday by POLITICO, asserts that U.S. sanctions on Iran are insufficient to convince the longtime U.S. adversary to eliminate its military presence in Syria. And it warns that while Israeli actions have slowed Iran’s progress in Syria, a wider Israeli-Iran confrontation remains a possibility.

“Iran remains undeterred in its strategy of entrenching itself in Syria,” the report states, adding that Tehran is integrating some of its forces into the Syrian regime’s army, cultivating Syria militias and continuing to transfer sophisticated weapons to Syria “with the objective of enhancing its regional power projection capabilities and threatening Israel.”

The Syria Study Group, housed at the U.S. Institute of Peace, was created by legislation spearheaded by Sen. Jeanne Shaheen (D-N.H.), who worked with the late Sen. John McCain (R-Ariz.) on the proposal. The interim report — produced by a dozen experts, each appointed by a member of Congress — was delivered to lawmakers earlier this month. The group’s final report is expected to be finished by September.

The findings so far are the latest reminder of deep bipartisan reservations within Congress about Trump’s hands-off attitude towards Syria, which he has said amounts to nothing more than “sand and death.”

The Republican president’s December order to withdraw American forces was a final straw leading to the resignation of his Defense secretary, James Mattis, and his special envoy for the fight against the Islamic State, or ISIS, Brett McGurk. It also led to a Senate rebuke of Trump led by Majority Leader Mitch McConnell, a fellow Republican.

The report warns that al-Qaida operatives remain active in the northwestern Syrian province of Idlib, where U.S. aircraft rarely venture due to Russian air defenses in the area. “ISIS is not the only terrorist threat emanating from Syria,” the report notes, explaining that al-Qaida “is in effective control of Idlib and retains the capacity to conduct external attacks.”

Syrian dictator Bashar Assad’s forces, backed by Russia, have in recent days used airstrikes and other means in moves apparently aimed at retaking Idlib. The violence threatens a Turkish-Russian negotiated ceasefire in the area that has kept the calm for months.

The report calls on the U.S. to reassert “involvement in diplomacy over the cease-fire.” It says Assad intends to retake all of Syria and is unwilling to accept political compromises, but adds that Assad’s present control over parts of the country remains tenuous.

The report asserts that the conflict in Syria has “enhanced Russian prestige in the region,” posing a long-term challenge to the United States. “Perceived success in Syria has emboldened Russia to seek to undermine U.S. influence in other parts of the region,” it states.

Like Iran, Moscow has put money and military muscle into supporting Assad. U.S. activities in Syria have been largely confined to battling terrorist groups, not Assad‘s regime.

The report says that Iran and Russia are “effective partners to one another and to the [Assad] regime,” but also says there are frictions among the three, and perhaps different long-term goals.

“Iran may prefer a chaotic Syria, which it can exploit for power projection. Russia prefers Syria’s stabilization and reintegration into the international community,” the Study Group says.

The group insists that the United States stick to its policy of isolating the Assad regime, including by discouraging other Arab governments from engaging with the strongman. It says the U.S. should withhold reconstruction funding from areas under Assad’s control, but that it should increase similar resources for areas the U.S. and its partners took back from the Islamic State.

The report also urges the United States to accept more Syrian refugees, sending an “important signal to both European allies and regional host countries” that have accepted numerous Syrians fleeing the violence.

Under Trump, the number of Syrian refugees taken in by the United States last year was just a few dozen, far less than the thousands accepted under the Obama administration. Trump has dramatically scaled down U.S. refugee resettlement, claiming — with little evidence — that refugees pose security risks.

The Syria Study Group is modeled in part after the Iraq Study Group, which was created in 2006 to recommend policy in the aftermath of the 2003 U.S. invasion.

The Syria Study Goup’s co-chairs are Dana Stroul, a Middle East expert previously on the staff of the Democratic wing of the Senate Foreign Relations Committee, and Michael Singh, a Middle East expert who served in the George W. Bush administration.