The United Nations told the leader of the Islamist Hayat Tahrir al-Sham (HTS) group which toppled the Bashar al-Assad regime that Syria must have a "credible and inclusive" transition.
The UN special envoy for Syria, Geir Pedersen who arrived in Damascus on Sunday, has met Ahmed al-Sharaa - also known by his nom de guerre Abu Mohammed al-Jolani- Pedersen's office said Monday in a statement on Telegram.
He also met interim prime minister Mohammed al-Bashir, it said.
Pedersen met them after Saturday's international meeting on Syria in Jordan, and stressed "the need for a credible and inclusive Syrian-owned and led political transition based on the principles of United Nations Security Council resolution 2254 (2015)," which was adopted in December 2015 and called for a ceasefire and political settlement in the country.
The UN envoy also underlined "the intention of the United Nations to render all assistance to the Syrian people", and was briefed on their "challenges and priorities", the statement added.
It said Pedersen had several engagements planned in the days ahead, but did not elaborate.
Assad was toppled by a lightning 11-day rebel offensive that swept down from northwest Syria, with fighters entering the capital on December 8.
Abandoned by his Russian and Iranian backers, Assad fled into exile in Moscow, bring to an end five decades of authoritarianism, abuse and Baathist rule by his clan.
The HTS group that led his overthrow is a former branch of Al-Qaeda in Syria, and the United States and other Western governments still classify it as a "terrorist" group.
While hailing Assad's downfall, several nations have said they will wait to see how Syria's new transitional government treats minorities in the multi-ethnic and multi-confessional country.
Bashir said last week that rights for all of Syria's religious groups will be "guaranteed" shortly after he was tasked with heading the transitional government.
Several countries including the United States and Britain have said they have already made contact with the HTS leader.