Secretary of State John Kerry is meeting with Russian Foreign Minister Sergey Lavrov in London on Friday in a last-minute attempt to resolve the crisis in Ukraine's Crimea region.

Ahead of the meeting, which began Friday morning at the American embassy residence in London known as the Winfield House, Kerry said he looked forward to delving into the matter to try to find a solution.

“Obviously, we have a lot to talk about,” Kerry said. “I look forward to the opportunity to dig into the issues and possibilities that we may be able to find about how to move forward together to resolve some of the differences between us. We look forward, I know, to a good conversation.”

Lavrov appeared more reticent in his brief remarks before negotiations began. He said he was “satisfied” to be meeting with Kerry but expressed concern about the late timing, which comes just 48 hours before a scheduled Sunday referendum vote in the Crimea region to secede from Ukraine and join the Russian Federation.

“I’m also satisfied to have this meeting today,” Lavrov said through an interpreter. “This is a difficult situation we are in. Many events have happened and a lot of time has been lost, so now we have to think what can be done.”

Throughout the past week, U.S. officials declined to meet with Russian counterparts unless Russia softened its stance in the Crimea region.

The two shook hands, but their brief public remarks were serious and lacked the easy camaraderie and smiles the two veteran diplomats had expressed before previous one-on-ones.

The meeting comes the day after Kerry gave Russia until Monday to reverse course in Ukraine or face serious repercussions from the U.S. and the European community.

U.S. and European officials argue that Moscow is orchestrating the referendum and waging an intimidation campaign with thousands of Russian troops controlling the region.

The Crimean regional parliament has already voted to secede and join the Russian Federation, and the population of Crimea, a majority of which is made up of ethnic Russians and current and former members of the Russian military, is expected to approve the referendum.

U.S. and its European allies argue that the vote violates Ukraine's territorial sovereignty and cannot be fair or legitimate because it is taking place in an area occupied by Russian troops. If the vote is approved, Kerry said the U.S. and Europe would not recognize it as legitimate under international law.

Kerry also has suggested that the U.S. and Europe on Monday would then unite to impose sanctions on Russia.

“There will be a response of some kind to the referendum itself,” Kerry said during a Senate hearing Thursday. “If there is no sign [from Russia] of any capacity to respond to this issue ... there will be a very serious series of steps on Monday.”

Over the last few days, reports that Russian troops have amassed at their border with Ukraine has alarmed Ukrainians stoking fears about further Russian military advances.

As a show of force, Russia also began military war games for its fighter and helicopters near the border, the Russian Interfax News agency reported Friday.

Russian authorities on Thursday tried to clamp down on any open public dissent, blocking access to several opposition websites, the Associated Press reported. But hackers soon retaliated by taking down the web sites of the Kremlin and the Russian central back.

With tensions mounting ahead of the vote, U.S. and European officials are preparing different contingency plans if Russian forces advance farther into the eastern area of Ukraine.

When asked during Thursday's hearing whether the U.S. would provide weapons to Ukrainians if Russia breaches its Eastern border, Kerry responded cautiously.

“We have contingencies — we are talking through various options that may or may not be available,” he said.

“Our hope is not to create hysteria or excessive concern about that at this point in time,” he said. “Our hope is to avoid that, but there's no telling that we can.”

U.S. authorities are closely monitoring the number of Russian troops in Crimea, as well as their movements, he said, noting that Moscow is allowed to have a total of 25,000 troops in Crimea.

He said that currently Russia does not have the assets positioned to “march in and take over all of Ukraine but that could change and we recognize that.”

“I've been impressed on how united our European allies are on this. … To a person, to a country, they are very, very committed to make sure there is accountability,” he said.