As it happened: US claims Russia could stage reason to invade Ukraine - BBC News
But Russia's deputy foreign minister says Western allegations of a false-flag plot are "baseless".
Image caption: The US embassy in Moscow

Russia delivered a list of demands to the US ambassador on Thursday, accusing Washington of ignoring its security demands.

“No ‘Russian invasion of Ukraine’, which the United States and its allies have officially been announcing since last fall, is happening, nor is one being planned,” says the letter from the Russian Foreign Ministry.

"In the absence of the readiness of the American side to agree on firm, legally binding guarantees of our security from the United States and its allies, Russia will be forced to respond, including through the implementation of military-technical measures," the lengthy document says.

It called the US refusal to commit to never allowing Ukraine to join Nato "not constructive" and called for Nato troops to pull back to countries that joined the alliance before 1997.

"We insist on the withdrawal of all US armed forces in Central Europe, Eastern Europe and the Baltics," it added.

The letter adds that Russia is prepared to negotiate on arms control treaties, and the possible Russian inspection of US missile bases in Poland and Romania, but only if its security concerns are addressed.

“We welcome the readiness of the United States for appropriate consultations,” the document says, adding: “This work cannot replace the settlement of the key problems posed by Russia.”

The US did not immediately respond to the list of demands.