Syrian President Bashar Assad will not step down at a proposed peace conference in Geneva but will only discuss the formation of a national unity government, the foreign minister said on Monday.

Speaking at a press conference in Damascus, Foreign Minister Walid al-Muallem also slammed a decision by supporters of the Syrian opposition to arm the rebels, saying it would only prolong a conflict already in its 28th month.

"President Bashar Assad will not resign. If your condition (for talks at Geneva) is President Assad's resignation, don't bother coming," he said.

"We will head to Geneva not to hand over power to the other side... We will go to Geneva in order to set up a real partnership and a broad national unity government."

Despite supporting opposing sides in the conflict, Russia and the United States have spearheaded an initiative to hold a peace conference in Geneva.

But prospects for the conference appear dim, and it has already been pushed back from a mooted June date until July at the earliest.

The opposition has said that any solution to the conflict must involve Assad's departure, something the regime has repeatedly ruled out.

The opposition has also set other conditions for its attendance, including the withdrawal of Hizbullah fighters from neighboring Lebanon who have intervened in support of the Assad regime.

The Syrian government has said it will attend the conference, but has made clear it has no plans to cede power.

Muallem also lashed out against a decision by the Friends of Syria group of Arab and Western governments that back the opposition to step up their assistance to the rebels.

"Two days ago a conference (of the Friends of Syria group) was held in Doha. They emerged with a clear decision to arm the opposition... This will only prolong the crisis," Muallem said.

Qatar said the Friends of Syria group had agreed on a "secret" plan to ramp up assistance to the rebels.

U.S. Secretary of State John Kerry pledged additional support for the rebels to end an "imbalance" in Assad's favor.

"Who decides when the balance needs to be restored?" asked Muallem.

"They say the restoration of balance is aimed at forcing the Syrian government to attend the Geneva talks. We said we are ready to attend -- but what about the other side?" he asked.

The Friends of Syria group "said they are acting for the sake of the Syrian people. Does killing the Syrian people achieve that goal?"

Muallem warned that any arms provided to the opposition would end up in the hands of Al-Nusra Front, a rebel group that has openly proclaimed its allegiance to Al-Qaida and is on Washington's terror blacklist.

"Why don't they (the Friends of Syria) see how they are contributing to terrorism?

"I only want to say that what was decided in Doha is dangerous because it aims at prolonging the violence, and it encourages terrorism," he said.

"Arming the opposition will be an obstacle to the Geneva conference and will kill more of our people."