By Patricia Zengerle

WASHINGTON (Reuters) - Republican and Democratic U.S. senators say it is too soon to consider lifting sanctions on Syria following the removal of President Bashar al-Assad, an indication that Washington is unlikely to change its policy any time soon.

"We're all really happy that Assad is gone," Senator Jim Risch, the top Republican on the Senate Foreign Relations Committee, told Reuters. "We worked at it for a long, long time, and the job is done. The problem is, what comes next?"

Hayat Tahrir al-Sham (HTS), a former al Qaeda affiliate that stormed across Syria and ousted Assad last week, is designated as a terrorist organization by the United States and most other countries, and also sanctioned by the United Nations.

"So, given that, it certainly calls for considerable pause, to watch and see what happens," he said, noting that while rebel leaders were making encouraging statements about unity and human rights, it remains to be seen how they act.

Risch will chair the foreign relations panel, which oversees U.S. diplomacy, starting in January when President-elect Donald Trump's fellow Republicans take control of the Senate.

Trump, who takes office on Jan. 20, said the United States should not be involved in the Syrian conflict.

Advocates say issuing waivers and licenses would encourage economic development and foreign investment, providing the rebels' new government with funding desperately needed to rebuild and establish government institutions.

FOCUS ON HUMAN RIGHTS

But opponents say the risk is too high until they are sure the rebels allow human rights, such as freedom of expression and religion, and do not attack members of minority groups.

Senior Democrats also called for caution.

"It's too early to tell whether the incoming regime's record will reflect a different way of doing business," Senator Ben Cardin, the current committee chairman, told a news conference.

And Senator Chris Murphy, who chairs the Senate's Middle East subcommittee, also said it was too soon to lift sanctions, given the rebels' history of terrorist ties, but stressed the importance of communicating with the new authorities in Syria at a time when world powers are jockeying for influence there.

"I do not think the United States should lock ourselves out of a room that everyone else is in," he told Reuters in a telephone interview, especially given the billions of dollars in assets and U.S. troop deployment in and around Syria.

"I don't think we should be shy about opening lines of communications," Murphy said.

Sanctions affect material support for Syria, but do not bar communications with its government.

There have been a few calls in Congress to ease sanctions, but the overwhelming sentiment is against doing so.

The House of Representatives on Wednesday passed the National Defense Authorization Act, or NDAA, which included an extension until 2029 of the "Caesar sanctions," which apply to business in Syria and any national dealing with Syria or Russian and Iranian entities in Syria.

The NDAA is expected to pass the Senate next week, sending it to the White House, where President Joe Biden is expected to sign it into law.

(Reporting by Patricia Zengerle, Editing by William Maclean)