Syrian President Bashar al-Assad is quoted as saying he has no intention of quitting, and the issue is not up for discussion at peace talks.
“If we wanted to surrender we would have surrendered from the start,” Mr Assad told Russian MPs in Damascus, according to Interfax news agency.
The government, opposition groups and Western diplomats will attend peace talks in Switzerland from Wednesday.
More than 100,000 have been killed and millions displaced in Syria’s conflict.
However, the Syrian presidency later said the comments reported by Interfax were “inaccurate”, without giving further details.
Opposition groups have previously demanded the removal of Mr Assad as a condition of any discussions on a possible transitional government.
But the Syrian National Coalition, the exiled opposition body, announced on Saturday that it would attend the talks.
The decision was praised by the US which, with Russia and the UN, is taking a leading role in organising the negotiations.
The path to the talks began in May last year when US Secretary of State John Kerry and Russian counterpart Sergei Lavrov agreed to try to bring both sides together.
Later, the UN Security Council called for a conference to implement the Geneva communique – a deal on a transitional government agreed at a UN-backed meeting in 2012.
Damascus agreed to take part in the talks, but said its delegation would pursue “first and foremost eliminating terrorism”.
Mr Assad is said to have reiterated that point of view in his talks with the Russian MPs.
The BBC’s Jim Muir in neighbouring Lebanon says his reported comments underline the gaping gulf between the regime and the opposition, and are clearly not going to improve the atmosphere before the talks.