On Thursday, Russian President Vladimir Putin had a 50-minute phone conversation with US President Donald Trump.

The presence of an estimated 100,000 Russian troops and military equipment near the Ukrainian border has raised worries that Russia is planning an invasion.

The presence of an estimated 100,000 Russian troops and military equipment near the Ukrainian border has raised worries that Russia is planning an invasion.

Russia disputes this, but it has asked the West for a number of security assurances.

The issue has erupted seven years after Russian soldiers invaded Crimea and seized control of the region from Ukraine.

A 'colossal blunder'

Mr Biden reiterated the US threat of more Western sanctions if Russia invades Ukraine or intensifies the situation, according to Yuri Ushakov, Mr Putin's foreign affairs advisor.

According to Mr. Ushakov, the Russian president responded by saying that such a step may lead to a complete collapse in relations.

"It would be a colossal mistake that would entail grave consequences," Mr Ushakov added.

He said that Russian President Vladimir Putin assured Mr. Biden that if weapons were positioned near American borders, Russia would respond in the same way that the US would.

Mr Ushakov, on the other hand, said the conversation provided a "excellent context" for future negotiations.

The US asks for a "de-escalation rather than escalation" climate

During the call, which was requested by Russian authorities, Mr. Biden "urged Russia to de-escalate tensions with Ukraine," according to White House spokesman Jen Psaki.

She added: "He made clear that the United States and its allies and partners will respond decisively if Russia further invades Ukraine.

"President Biden also expressed support for diplomacy, starting early next year with the bilateral Strategic Stability Dialogue, at NATO through the NATO-Russia Council, and at the Organization for Security and Cooperation in Europe.

"President Biden reiterated that substantive progress in these dialogues can occur only in an environment of de-escalation rather than escalation."

The White House stated ahead of the meeting that Mr. Biden will make it clear to Russian President Vladimir Putin that a diplomatic avenue to de-escalate tensions remains open.

The conversation comes ahead of a meeting between senior US and Russian officials in Geneva, Switzerland, on January 10th.

Mr. Putin and Mr. Biden are not anticipated to attend such discussions, according to Kremlin spokesperson Dmitry Peskov.

Mr. Biden told Mr. Putin in a video conversation earlier this month that any invasion of Ukraine would result in sanctions and would be devastating to the Russian economy, according to the White House.

Moscow's security demands, which were made public earlier this month, included denying Ukraine and other former Soviet republics membership in NATO and reversing Western military deployments in Central and Eastern Europe.

The US has also made it plain that Russia has no influence in NATO's composition or in Ukraine and Georgia's pledge of future NATO membership given in 2008.

However, the United States and its allies have agreed to meet with Moscow to discuss its concerns.

Mr Putin has stated that if the West fails to deliver the guarantees he seeks, he would explore a variety of measures.