Kerry meets Syrian opposition leader in Rome

World powers were to hold key talks with the Syrian opposition in Rome on Thursday after Washington suggested it was ready to boost support to rebels battling President Bashar al-Assad's regime.

Ahead of The Friends of Syria meeting in the Italian capital, the new US Secretary of State John Kerry met with Syrian opposition leader Ahmed Moaz al-Khatib.

Kerry has said that the Syrian opposition needs "more help" in the fight against Assad and that Washington wants to speed up the crisis-hit country's political transition.

The Rome talks come two days before an important meeting of the main opposition National Coalition on Saturday in Istanbul, where the umbrella group is to elect a prime minister and government to run parts of Syria seized from Assad's control.

Momentum has been building ahead of Thursday's Rome talks, with the opposition -- which initially vowed a boycott -- lured back to the 11-nation meeting after the US and Britain promised specific offers of help.

In Paris as part of a European tour on Wednesday, Kerry made it clear Washington was ready to step up its support for the opposition.

"We are examining and developing ways to accelerate the political transition that the Syrian people seek and deserve, and that is what we will be discussing in Rome," Kerry said.

He said he wanted to hear from opposition leader Khatib about how best to end the violence in Syria, where the United Nations says at least 70,000 have died and hundreds of thousands have been uprooted in the two-year conflict.

"That may require us to change president Assad's current calculation. He needs to know he can't shoot his way out of this," Kerry said. "I think the opposition needs more help in order to be able to do that and we are working together to have a united position."

Kerry said there was a desire to help the opposition deliver assistance and basic services in areas it has "liberated from the regime".

In Moscow, French President Francois Hollande said ahead of a meeting with Russian counterpart Vladimir Putin that a political solution to the Syrian crisis was possible within weeks.

"I think that in the next few weeks we will manage to find a political solution that will stop the conflict from escalating," Hollande told Echo of Moscow radio station in comments translated into Russian.

The Washington Post reported Wednesday that the White House was considering a policy shift to supply rebels with "non-lethal" aid, including armoured vehicles and perhaps even military training.

A US State Department official refused to confirm the report, but said Washington wanted to help the opposition maintain "the institutions of the state" in areas under their control.

"We're talking about basic services, water, electricity -- but also (to) build up new institutions in terms of governance, rule of law, police," State Department deputy acting spokesman Patrick Ventrell told reporters.

Prominent Republican US Senator Marco Rubio has urged the United States to provide ammunition to Syrian rebels and share intelligence, but only with "responsible" groups.

"What the opposition really needs is access to ammunition," he said in Washington. "Ammunition is something we can provide which is not weaponry per say, but is essential."

Rubio also warned that the best-organised and best-armed rebel groups in Syria "are the most radical ones, the most anti-democratic ones, the most anti-American ones."

"The real risk is that when Assad falls -- and he will fall -- the largest, those well-equipped, best-organised groups in that conflict, will be the people that quite frankly are against our national interest."

The United States and its Western allies are keen to back moderate elements among the political opposition and fighters on the ground, amid fears that increasingly powerful Islamic extremist groups are taking a prominent role in Syria's uprising.

Thursday's Rome talks will also provide some measure of whether the opposition is ready to consider any form of talks with regime.

Pressure has been building for talks on ending the crisis, with Russia, Assad's most powerful supporter, this week urging both sides to sit down for negotiations.

The Syrian conflict, which has killed at least 70,000 people since erupting in March 2011, has shown no signs of slowing down, with fierce battles on Wednesday rocking towns near the capital Damascus.