US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov will hold last-ditch talks on Ukraine’s Crimea region in London today, just 48 hours before its breakaway referendum.

Kerry says the United States and European Union will take serious steps against Moscow if the vote results in Russian annexation, according to Euronews.

His latest warning came as Ukraine’s interim Prime Minister Arseny Yatsenyuk addressed the UN Security Council in New York.

“We urge the Russian Federation to pull back its military forces deployed in Crimea to barracks and to start real talks and negotiations,” he said.

Continuing in Russian, Yatsenyuk asked whether Russia wanted war.

“I’ll give a direct answer; Russians don’t want war,” said Moscow’s ambassador to the UN, Vitaly Churkin. “We don’t want to escalate the situation.”

The United States has circulated a draft resolution that would declare Sunday’s planned referendum illegal. But Russia, one of the Security Council’s five veto-wielding permanent members, has made it clear it opposes the draft.