Syria's president has said he will not accept any solution to his country's crisis imposed from outside, as major powers prepare to meet in Geneva.
Bashar al-Assad told Iranian television it was an "internal issue which has nothing to do with foreign countries".
No amount of foreign pressure would make his government change its policy on internal security, he added.
Russia meanwhile insisted it would not endorse a plan for a transition that would require Mr Assad to step down.
Foreign Minister Sergei Lavrov said: "We will not support and cannot support any meddling from outside or any imposition of recipes. This also concerns the fate of the president of the country, Bashar al-Assad."
Syrian opposition groups have said the president would have to hand over power and leave the country as part of any settlement.
Mr Lavrov is due to meet US Secretary of State Hillary Clinton in St Petersburg later on Friday in an effort to agree a consensus formula to end the bloodshed in Syria.
Saturday's conference in Geneva was called by the UN and Arab League envoy, Kofi Annan, as the violence intensified in Syria. The UK-based Syrian Observatory for Human Rights reported that about 3,000 people have been killed so far this month.
Mr Annan has said the meeting will only convene if he is sure all the countries attending will unite around his plan. On Friday, a spokesman said he remained "optimistic" and that the talks were "on course".
Those invited include the five permanent members of the UN Security Council, as well as Turkey, Iraq, Kuwait and Qatar. Iran and Saudi Arabia will not be there, with Western countries objecting to the former's presence and Russia to the latter's.
Mr Annan wants support for an interim government that could include opposition members and officials serving under Mr Assad, but exclude those "whose continued presence and participation would undermine the credibility of the transition and jeopardise stability and reconciliation".
Diplomats said this was an implicit reference to the Syrian president.
Russia initially signalled to Mr Annan that his plan was acceptable, but Mr Lavrov appeared to reverse course with his comments on Thursday.
In an interview with Iranian state television broadcast on Thursday evening, Mr Assad spelled out that the regime would not accept any outside solution, even if it came from friendly countries.
The answer had to come from the Syrians themselves, he said, because "no-one knows how to solve Syria's problems better than we do".
"The real issue is maintaining national unity in the country. We need to overcome the internal differences and disagreements," he said.
"Foreign pressure will not have an influence on our stance," he added. "We have been under pressure for a long time, and it did not have an effect in the past, and it will not have any influence in the future."
The BBC's Jim Muir in Beirut says the president seemed confident that in any eventuality, there would be no Western intervention as in Libya, where he believed the situation was now worse than before the overthrow of Muammar Gaddafi.
As for the internal situation, Mr Assad made it clear that the drive against armed rebels would continue, our correspondent adds.
"The responsibility of the Syrian government is to protect all of our residents. You have a responsibility to annihilate terrorists in any corner of the country," Mr Assad said.
"When you eliminate a terrorist, it's possible that you are saving the lives of tens, hundreds, or even thousands," he added.
Our correspondent says the Syrian leader's message to intensifying international diplomacy seemed clear - that it was a waste of time.