LONDON (AP) — With little hope of halting a vote to separate a strategic Ukraine peninsula from the rest of the country, the West is readying to impose harsh sanctions on Russia for what U.S. officials described as Moscow’s insistence in undermining the new upstart government in Kiev, and fueling tensions among those who oppose it.

U.S. Secretary of State John Kerry flew to London on Friday to meet with Russian Foreign Minister Sergey Lavrov in a last-minute bid to stave off a new chapter in the East-West crisis over Ukraine. On Sunday, Ukraine’s pro-Russian Crimea region will vote whether to secede, and perhaps join Russia, in anger over new leaders in Kiev who seek to forge stronger economic ties with Europe.