"No time has been set, and the factors are not yet in place if we want (the US-Russian initiative dubbed Geneva 2) to succeed," Assad told Lebanese television channel Al-Mayadeen on Monday.
"Which forces are taking part? What relation do these forces have with the Syrian people? Do these forces represent the Syrian people, or do they represent the states that invented them?" Assad asked in typically defiant fashion.
In the lengthy interview, Assad also said he was willing to run for re-election in 2014, in remarks that came soon after US Secretary of State John Kerry said that if he were to win, it would extend Syria's civil war. "Personally, I don't see any reason why I shouldn't run in the next election," Assad declared.
Kerry's comments came before a "Friends of Syria" meeting in London with Syrian opposition leaders, whom the US top diplomat said would never agree to Assad staying in power.
"He has bombed and gassed people in his country.... How can that man claim to rule under any legitimacy in the future?", Kerry said after talks with Arab League officials in Paris.
Assad accused Saudi Arabia of conducting the work of the United States in Syria and also demanded that the UN-Arab League envoy to Syria, Lakhdar Brahimi, stick to his mandate and not follow orders from other countries. Brahimi is currently on a tour of the Middle East to drum up support for the peace conference.
On Monday in Baghdad the envoy told reporters that all countries "with interests and influence in the Syrian affair must participate" in the Geneva conference.
The veteran troubleshooter has said he will also travel to Qatar, Turkey, Iran, Syria and then Geneva for talks with Russian and US representatives.
A pro-regime daily in Syria said Brahimi was expected this week in Damascus, where he came under heavy criticism from the regime for suggesting a transitional government after his last visit in 2012.
In the interview, Assad also denounced as "terrorists" the Muslim Brotherhood movement -- whose members are a main component of Syria's main opposition bloc, the Western and Arab-backed National Coalition.
"The solution must be a Syrian solution, regardless of whether foreign powers recognise it. It's doesn't matter. What matters is that the Syrian people recognise it," he said.
The Syrian government has been battling to crush a 31-month rebellion triggered by his forces' bloody crackdown on Arab Spring-inspired democracy protests. More than 115,000 people are believed to have been killed in the conflict.
Assad's comments were broadcast as his forces pressed on with deadly strikes against rebel-held areas, despite the flurry of diplomatic efforts to hold the proposed Geneva talks next month.
The United States and Russia have been trying to organise the conference on the heels of the deal they reached for the destruction of Syria's chemical weapons.
On Monday, the head of an international mission to carry out that task arrived in Syria, a statement said.
"Today, the Special Coordinator, Ms Sigrid Kaag arrived in Damascus," to lead a joint mission of the United Nations and the Hague-based Organisation for the Prohibition of Chemical Weapons.
The Dutch UN official leads a team tasked with inspecting more than 20 sites by the end of the month and destroying Syria's chemical stockpiles by mid-2014 under the landmark US-Russian deal.
The opposition has been fiercely critical of the agreement -- which averted US strikes against the regime following a sarin gas attack in August that killed hundreds of people -- and at least one major faction, the Syrian National Council, has already refused to go to Geneva.
The National Coalition umbrella opposition group, which includes the SNC, on Monday said it had postponed internal meetings to early November, as it weighs whether to attend the Geneva talks.
As diplomats wrangled over the talks, government forces killed a rebel commander, Lieutenant Colonel Yasser Abbud, during clashes at Tafas, in the southern province of Daraa, sources on both sides said. Daraa is the birthplace of an uprising that erupted in March 2011 and flared into the civil war.
News of the commander's death came as regime forces attempted to blunt a rebel offensive around the town of Mleha, southeast of Damascus, said the Syrian Observatory for Human Rights.
Four rockets were also launched from Syria into the eastern Lebanese town of Hermel, a stronghold of the powerful Hezbollah movement that is fighting alongside Assad's forces in their bid to crush the rebellion.