MOSCOW/GENEVA (Reuters) – U.S. Secretary of State John Kerry is expected to press President Vladimir Putin on how Russia sees a future political transition in Syria and the fate of President Bashar al-Assad.

With a fragile truce in place in Syria and warring sides attending peace talks in Geneva, Kerry wants to “get down to brass tacks” on the question of Assad’s future, a State Department official said.

While the United States want Assad to step aside, Russia says only the Syrian people can decide his fate at the ballot box and has bristled at any talk of regime change.

Kerry is holding talks with Putin at the Kremlin on Thursday, in a meeting arranged after the Russian leader’s surprise announcement on March 14 that he was partially withdrawing his forces from Syria.

“The Secretary would like to now really hear where President Putin is in his thinking … on a political transition” in Syria, the official said as Kerry arrived in Moscow.

“Obviously what we are looking for, and what we have been looking for, is how we are going to transition Syria away from Assad’s leadership,” the official said, speaking on condition of anonymity.

After five years of conflict that has killed over 250,000 people and caused the world’s worst refugee crisis, Washington and Moscow reached a deal three weeks ago for a cessation of hostilities and delivery of humanitarian aid to besieged areas.

The State Department official said meetings with Putin and Foreign Minister Sergei Lavrov would evaluate the status of the ceasefire and try to “get on the same page” about ending violations and increasing humanitarian assistance.

UNILATERAL THREAT

Russia this week threatened to act unilaterally against those who violate the ceasefire unless it reached a deal with the United States on ways to detect and prevent truce breaches.

The Syrian opposition has accused government forces of renewing sieges and stepping up a campaign of barrel-bombing across the country.

In Geneva, where warring sides are a week into talks on ending the conflict, government officials have rejected any discussion on the fate of Assad, who opposition leaders say must go as part of any transition.

Kremlin spokesman Dmitry Peskov said the Syria peace talks were always going to be long and difficult, and it was too early to talk about patience running out on any side.

U.N. Special Envoy for Syria Staffan de Mistura said on Tuesday he hoped the U.S-Russia meeting would give an impetus to the peace talks where the divisive issue of a political transition is stalling progress.

But the State Department official played down expectations that the meeting would have an immediate impact on the talks, which adjourn on Thursday with the next round expected in early April.

A Syrian activist at the talks, Jihad Makdissi, said de Mistura was planning to issue a paper on a “potential common vision”.

The Syrian government delegation said the U.N. envoy had handed them a document which they would study on their return to Damascus. No details of either paper were disclosed.

However, the United Nations said the Syrian government had given verbal assurances that aid convoys can go into three or four areas that its forces are besieging.

U.N. humanitarian adviser Jan Egeland said the United Nations had been allowed to enter eight or nine of the 11 areas it had asked to supply with aid, including three or four besieged areas.

But it had not been allowed to go into the town of Daraya, where the World Food Programme has said some people have been reduced to eating grass.

PALMYRA OFFENSIVE

On the battlefield, Syrian government forces and their allies were reported to have pushed forward against Islamic State fighters to reach the outskirts of the historic city of Palmyra on Wednesday.

State news agency SANA quoted a military source who said the army and allied militia advanced in the hills outside Palmyra and toward a road junction “after eliminating the last terrorist Daesh groups there”, referring to Islamic State fighters. Islamic State is not covered by the truce agreement.

The Syrian army is trying to recapture Palmyra, which Islamic State seized in May, to open a road to the mostly IS-held eastern province of Deir al-Zor.

Clashes raged around Palmyra after government forces took control of most of a nearby hill with air cover from Syrian and Russian warplanes, the British-based Syrian Observatory for Human Rights said.

Russia has withdrawn around half of its air force in Syria, according to Reuters calculations based on state TV footage, some of which was not broadcast.

But Moscow has maintained a group of Su-24 bombers at its Latakia air base and deployed a number of advanced attack helicopters, meaning it is able to continue a reduced number of air strikes in the country.

Operating from Russia’s Shayrat air base southeast of Homs, the helicopter force will be used to secure territory gains around Aleppo and support the Syrian army offensive against Islamic State in Palmyra, Western officials said.

(Additional reporting by Dmitry Solovyov, Jack Stubbs, John Davison, Dominic Evans, Stephanie Nebehay and Tom Miles; Writing by Giles Elgood, editing by Peter Millership)