US Secretary of State Antony Blinken and Russian Foreign Minister Sergei Lavrov are to hold talks in Geneva later amid mounting fears that Russia could be about to invade Ukraine.

On Thursday Mr Blinken warned Moscow of grave consequences if any of its forces crossed the border.

Russia has 100,000 troops at the border, but denies planning to invade.

President Vladimir Putin has insisted that Ukraine should never be allowed to join Nato.

He also wants the defensive alliance to abandon military activity in eastern Europe.

The summit between the top US and Russian diplomats follows moves by Mr Blinken to shore up support among US allies for sanctions against Mr Putin's regime. 

Following discussions in Berlin with British, French and German officials, Mr Blinken said on Thursday that allowing a Russian incursion into Ukraine would "drag us all back to a much more dangerous and unstable time, when this continent, and this city, were divided in two... with the threat of all-out war hanging over everyone's heads".

State Department officials have said that Mr Blinken will seek to offer Mr Lavrov a "diplomatic off-ramp" to ease tensions. 

Speaking alongside Mr Blinken, Germany's new Foreign Minister Annalena Baerbock pledged immediate action against any Russian invasion and did not rule out imposing measures that "could have economic consequences for ourselves".

The UK's Foreign Secretary Liz Truss has also called on Mr Putin to "desist and step back from Ukraine before he makes a massive strategic mistake" that would lead to terrible loss of life. 

During a speech on Friday in Sydney, she urged Western powers to "step up" and warned that autocratic nations were being "emboldened in a way we haven't seen since the cold war". 

Earlier this week, Britain announced it was supplying Ukraine with extra troops for training and defensive weapons.