U.S. authorities have warned Russia not to invade Ukraine and urged both countries to return to a set of agreements designed to end a separatist war by Russian speakers in eastern Ukraine.
Here is a look at the agreements, which were signed in Minsk in 2014 and 2015.
MINSK I
Ukraine and the Russian-backed separatists agreed a 12-point ceasefire deal in the Belarusian capital in September 2014.
Its provisions included prisoner exchanges, deliveries of humanitarian aid and the withdrawal of heavy weapons, five months into a conflict that had by then killed more than 2,600 people - a toll that Ukrainian President Volodymyr Zelenskiy says has since risen to around 15,000.
The agreement quickly broke down, with violations by both sides.
MINSK II
Representatives of Russia, Ukraine, the Organisation for Security and Cooperation in Europe (OSCE) and the leaders of two pro-Russian separatist regions signed a 13-point agreement in February 2015.
The leaders of France, Germany, Russia and Ukraine, gathered in Minsk at the same time, issued a declaration of support for the deal.
It set out military and political steps that remain unimplemented. A major blockage has been Russia's insistence that it is not a party to the conflict and therefore is not bound by its terms.
Point 10, for example, calls for the withdrawal of all foreign armed formations and military equipment from the two disputed regions, Donetsk and Luhansk: Ukraine says this refers to forces from Russia, but Moscow denies it has any forces there.
The 13 points were, in brief:
1. An immediate and comprehensive ceasefire
2. Withdrawal of all heavy weapons by both sides
3. Monitoring and verification by the OSCE
4. To start a dialogue on interim self-government for the Donetsk and Luhansk regions, in accordance with Ukrainian law, and acknowledge their special status by parliamentary resolution.
5. A pardon and amnesty for people involved in the fighting
6. An exchange of hostages and prisoners.
7. Provision of humanitarian assistance.
8. Resumption of socio-economic ties, including pensions.
9. Restoration of full control of the state border by the government of Ukraine.
10. Withdrawal of all foreign armed formations, military equipment and mercenaries.
11. Constitutional reform in Ukraine including decentralisation, with specific mention of Donetsk and Luhansk.
12. Elections in Donetsk and Luhansk on terms to be agreed with their representatives.
13. Intensifying the work of a Trilateral Contact Group comprising representatives of Russia, Ukraine and the OSCE.
(Writing by Mark Trevelyan; editing by Philippa Fletcher and John Stonestreet)
