US President Joe Biden has called on all American citizens remaining in Ukraine to leave the country immediately, saying he won’t send troops to rescue Americans trapped there if Russia invades the country.

Citing increased threats of Russian military action, Biden warned that “things could go crazy quickly” in the region.

Russia has repeatedly denied any plans to invade Ukraine despite massing more than 100,000 troops near the border. But it has just begun massive military drills with neighbouring Belarus, and Ukraine has accused Russia of blocking its access to the sea by conducting Naval drills.

According to the Kremlin it wants to enforce “red lines” to make sure that its former Soviet neighbour does not join Transatlantic alliance, NATO.

The US State Department on Thursday, February 10 urged Americans in Ukraine to leave immediately.

Biden has now reiterated that stance.

“American citizens should leave now,” Biden told NBC News.

“We’re dealing with one of the largest armies in the world. It’s a very different situation and things could go crazy quickly.”

Asked whether there was a scenario that could prompt him to send troops to rescue fleeing Americans, Biden replied:

“There’s not. That’s a world war when Americans and Russia start shooting at one another. We’re in a very different world than we’ve ever been.”

Russia and Ukraine announced late on Thursday February 10, that they had failed to reach any breakthrough after nine hours of talks with French and German officials aimed at ending the separatist conflict in eastern Ukraine. Ukrainian envoy Andriy Yermak said while there were disagreements “there is a will to continue and there is a will to negotiate”.

The current tensions come eight years after Russia annexed Ukraine’s southern Crimea peninsula. Since then, Ukraine’s military has been locked in a war with Russian-backed rebels in eastern areas near Russia’s borders.