US diplomats are in the Syrian capital Damascus where they plan to meet representatives from Hayat Tahrir al-Sham (HTS), the group now in charge but which Washington still designates as a terrorist organisation.
The visit follows those of delegations in recent days from the UN and other countries including the UK, France and Germany.
This is the first formal American diplomatic appearance in Damascus in more than a decade.
It is a further sign of the dramatic shifts under way in Syria since the fall of the President Bashar al-Assad's regime more than a week ago, and the speed of efforts by the US and Europe, also leaning on Arab countries, to try to influence its emerging governance.
The delegation of senior officials includes Assistant Secretary of State Barbara Leaf, Roger Carstens, who is US President Joe Biden's hostage envoy and Daniel Rubinstein, senior adviser in the Bureau of Near East Affairs.
"They will be engaging directly with the Syrian people, including members of civil society, activists, members of different communities, and other Syrian voices about their vision for the future of their country and how the United States can help support them," a State Department spokesperson said in a statement.
They plan to meet representatives from HTS, in a show of readiness to deal with the group the US still designates as a terrorist organisation, but building pressure for it to transition to inclusive, non-sectarian government.
Washington is effectively laying down a set of conditions before it would consider delisting the group - a critical step which could help ease the path towards sanctions relief that Damascus desperately needs.
The officials are seeking further information to help find the American journalist Austin Tice, who was abducted in Damascus in 2012.