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.