By Maya Gebeily

DAMASCUS (Reuters) - Two U.S. congressmen have urged senior American officials to suspend some sanctions on Syria to ease pressure on its shattered economy after the overthrow of Bashar al-Assad, according to a letter dated Dec. 10 and seen by Reuters.

The move is the latest effort in the West to push for easing sanctions after rebels led by Hayat Tahrir al-Sham (HTS), a former al Qaeda affiliate, swept into Damascus. A British minister said on Monday that Britain could rethink its designation of HTS as a banned organisation.

The letter to U.S. Secretary of State Antony Blinken, Treasury Secretary Janet Yellen and National Security Adviser Jake Sullivan was signed by Republican Representative Joe Wilson, who chairs the House Foreign Affairs Subcommittee on the Middle East and Democratic Representative Brendan Boyle, who chairs th Free Syria Caucus.

The letter acknowledges the possible extension for five more years of the Caesar sanctions, which apply across Syrian business sectors and to any national dealing with Syria or with Russian and Iranian entities in Syria.

Wilson and Boyle wrote that sanctions denied Assad the resources to sustain his military and ultimately contributed to its collapse - first in the northern city of Aleppo on Nov. 29 and in a string of losses until Damascus was seized on Dec. 8

The lawmakers wrote that while keeping sanctions on former government officials was important, they believed "that other parts of the legislation - such as sectoral sanctions and sanctions related to reconstruction - should be suspended".

The letter said the U.S. must issue waivers and general licenses to encourage economic development and foreign investment and "build good will" without impacting sanctions on designated terrorist groups.

Hayat Tahrir al-Sham, the Syrian rebel group that spearheaded the offensive that toppled Assad and whose civilian branch has been installed as a transitional government, is designated as a terrorist group by the United States and most other countries, as well as the United Nations.

Its new government has told business leaders it will adopt a free-market model and integrate the country into the global economy, Reuters reported on Tuesday.

"A deliberate and phased approach is required to unwind sanctions and export controls against Syria," the letter by Wilson and Boyle said, including "to incentivize the transitional government's compliance with international norms".

A source close to HTS told Reuters on Tuesday that the group was in touch with U.S. officials on lifting parts of the Caesar Sanctions.

"All of the obstacles facing the Syrian people and their future should be removed," the source said.

Another senior European diplomat told Reuters other states were pushing for broad humanitarian exemptions, much like the months-long waivers that were installed after the devastating 2023 earthquake to allow urgent aid to come in to Syria.

The diplomat said it was "too early" to drop all sanctions altogether given HTS's prominent role in government.

(Reporting by Maya Gebeily; Editing by Angus MacSwan)