British forces are preparing to travel to Ukraine in July to join allies in a peacekeeping training exercise.

The troops will be part of a group of about 1,300 troops, mostly American, who are taking part in Rapid Trident, a previously planned exercise.

US officers cancelled a military exercise in Russia in the light of current events but confirmed the exercise in Ukraine would go ahead.

British officials said they had yet to decide the UK's level of participation in Ukraine but confirmed planning for Rapid Trident 2014 in Lviv, near the Polish border, was ongoing.

The US has already sent 12 warplanes and 300 personnel to Poland in the wake of Russia's takeover of Crimea.

On Tuesday, vice president Joe Biden reassured Poland and the Baltic states that the US would protect them from any Russian aggression similar to what occurred in Crimea.A Ministry of Defence spokeswoman said: "Rapid Trident is a well-established annual US/Ukraine multinational exercise, which is routinely staged in Lviv, under the auspices of the Ukraine Armed Forces' International Peacekeeping and Security Training Centre. The UK did participate last year but no final decisions have yet been taken on the level of our participation this year."

The US cancelled Atlas Vision 2014, which was to take place in July in Chelyabinsk, in north-eastern Russia, in response to Russia's actions in Crimea.

Rapid Trident 2014 is to "promote regional stability and security, strengthen partnership capacity and foster trust while improving interoperability between the land forces of Ukraine, and Nato and partner nations, " according to the US forces in Europe website.

In addition to US and UK troops, Rapid Trident 2014 will include units from Armenia, Azerbaijan, Bulgaria, Canada, Georgia, Germany, Moldova, Poland, Romania and Ukraine.

Last year's exercise lasted two weeks and included about 1,300 troops. It focused on "airborne and air-mobile infantry operations," according to a report on the Rapid Trident website.