Syria has sacked deputy prime minister Qadri Jamil, who according to reports met with US officials over the weekend without government permission, the official SANA news agency said.
US and Middle East officials told the Reuters news agency that Jamil met US pointman for Syria, and former American Ambassador to the country, Robert Ford in Switzerland at the weekend to discuss the proposed "Geneva 2" talks.
The talks are aimed at launching negotiations between Syria's government and the rebel movement seeking its removal.
"Jamil was dismissed because he left his centre of work without prior permission and did not follow up on his duties ... Additionally, he undertook activities outside the nation without coordinating with the government," a statement posted on Syria TV said.
UN-Arab League envoy Lakhdar Brahimi, who is in Damascus meeting with Syrian officials to build support for the talks and is expected to meet Assad on Wednesday, said on Tuesday that it was up to Syrians to shape their political transition in any peace talks and warned of the potential "Somalisation" of the country.
In brief remarks to reporters outside a Damascus hotel, Brahimi insisted the Geneva talks would be "between the Syrian parties, and it is the Syrian parties who will determine the transitional phase and what comes after, not me."
Western countries and the UN have been pushing for Syria's warring parties to meet at a conference in Geneva to try to negotiate a settlement to the three-year conflict.
Assad has said in principle that his government will attend talks, but it will not negotiate with the country's disparate armed rebel groups. Syria's fractured opposition does not have a united stand on attending. A key sticking point is Assad's future.
Syria's conflict began as a peaceful protest movement against four decades of Assad family rule, but has degenerated into a civil war that has killed more than 100,000 people.