The US has scrapped a $10m (£7.9m) reward for the arrest of Syria's de facto leader Ahmed al-Sharaa, following meetings between senior diplomats and representatives from Hayat Tahrir al-Sham (HTS).
Assistant Secretary of State Barbara Leaf said the discussion with Sharaa was "very productive", and he came across as "pragmatic".
The US delegation arrived in the capital, Damascus, after HTS overthrew the Bashar al-Assad regime less than a fortnight ago. Washington still designates it as a terrorist group.
A State Department spokesperson confirmed that the diplomats discussed "transition principles" supported by the US, regional events and the need to fight against IS.
The spokesperson also said the officials were seeking further information on American citizens who disappeared under Assad's regime, including journalist Austin Tice, who was abducted in Damascus in 2012, and psychotherapist Majd Kamalmaz, who disappeared in 2017.
A US embassy spokesperson earlier said a news conference involving Ms Leaf had been cancelled due to "security concerns".
However during a later briefing, Leaf denied that, insisting "street celebrations" were the cause of the delay.
The visit 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 ousting of Assad, and the speed of efforts by the US and Europe, also leaning on Arab countries, to try to influence its emerging governance.
The visit follows those of delegations in recent days from the UN and other countries including the UK, France and Germany.
The delegation of senior officials includes Barbara Leaf, Roger Carstens, who is US President Joe Biden's hostage envoy, and Daniel Rubinstein, a senior adviser in the Bureau of Near East Affairs.
The spokesperson also said the delegation engaged with civil society groups and members of different communities in Syria "about their vision for the future of their country and how the United States can help support them".
The meeting was a show of readiness to deal with HTS, which the US still designates as a terrorist organisation but is 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.
Meanwhile, US Central Command (CENTCOM) confirmed that IS leader Abu Yusif and two of his operatives had been killed in an air strike in the Deir al-Zour province of north-eastern Syria.
It said in a statement on Friday that the airstrike was launched on Thursday and carried out in an area that was formerly controlled by the Assad regime and Russian forces supporting his government.
CENTCOM commander Gen Michael Erik Kurilla said the US would not allow IS "to take advantage of the current situation in Syria and reconstitute", adding the group intended to free more than 8,000 detained IS militants being held in Syria.
North America correspondent Anthony Zurcher makes sense of US politics in his twice weekly US Election Unspun newsletter. Readers in the UK can sign up here. Those outside the UK can sign up here.