Russia's foreign minister on Wednesday accused Ukrainian's government of dragging its feet on implementing last year's cease-fire agreement as Moscow sought to press its point in a new round of high-level diplomacy.

Fighting in Ukraine's industrial heartland, which has close ties to Russia, has killed more than 9,100 people and left large swaths of land under rebel control. Germany, France and Russia mediated talks between representatives of the Ukrainian government and Russia-backed separatists at talks in Minsk, Belarus, which resulted in a broad cease-fire agreement.

That has largely held, but none of the political elements, including calling a local election, has been implemented.

Foreign Minister Sergey Lavrov, who was hosting German counterpart Frank-Walter Steinmeier in Moscow, told reporters that Kiev's inaction is the main stumbling block to a peace settlement in the east. Lavrov said Germany had floated the idea of holding an election in the rebel-occupied territories this summer but Kiev said no.

"Minsk-2 cannot be reviewed, and we should resist attempts to undermine it," Lavrov said.

Kiev insists it can't hold the vote because it cannot guarantee security for election officials. Rebels in their turn have said they won't allow Ukrainian right-wing parties to run, which the Ukrainian government says makes the election impossible.

Steinmeier on Wednesday urged both sides to comply with the partial withdrawal and warned of a possible escalation.

He and Lavrov appeared to be in a jovial mood, with Steinmeier saying they both pledged to "look for ways to overcome the differences that stand in our way to find a solution" for eastern Ukraine.

Steinmeier also met with Russian President Vladimir Putin, who said at the start of the talks that they should discuss "horrible, tragic events in Belgium" along with other issues. Steinmeier noted the progress achieved in Syria and emphasized the need for joint action against terrorism.

Steinmeier's visit to Moscow opens a day of top diplomacy at the Russian capital, with U.S. Secretary of State John Kerry arriving later for talks on Ukraine and Syria. Steinmeier and Kerry are to have a private dinner late Wednesday before Kerry meets with Lavrov and President Vladimir Putin on Thursday.

U.S. officials said Kerry wanted to raise concerns about a recent sharp increase in cease-fire violations and press Russia to do more to get the separatists in line. Unless there is "true quiet" and full access for cease-fire monitors, the officials said it would be difficult to get progress on other parts of the Minsk deal.

Kerry will also raise the case of Nadezhda Savchenko, a Ukrainian pilot who was sentenced to 22 years in prison in Russia on Tuesday on charges the U.S. says are false. Savchenko was convicted of complicity to murder in the 2014 deaths of two Russian journalists in eastern Ukraine, opening a door to a possible prisoner swap between the two countries.

The U.S. has repeatedly called for Savchenko, who is also a member of parliament, to be released and did so again on Tuesday. Ukraine has suggested trading two Russian prisoners for Savchenko and the U.S. officials said Kerry would encourage Russia to accept the proposal.

On Syria, Kerry will be seeking clarity from Putin and Lavrov as to where Russia stands on a political transition for Syria, particularly on the future of President Bashar Assad, the officials said.