US President Joe Biden said on Wednesday that sending US forces to defend Ukraine from Russia was "out of the question" because it is not a member of the North Atlantic Treaty Organization (NATO), but said he had warned his Russian counterpart, Vladimir Putin, of unprecedented sanctions.

A day after the US and Russian presidents held a video summit, Biden told reporters at the White House that he had told Putin that the United States would respond with economic sanctions "the likes of which he had never seen" if Russia invaded neighboring Ukraine.

In addition to economic sanctions, Biden indicated that Russia's attack on Ukraine would be followed by the strengthening of its military presence in NATO regions in eastern Europe, and stressed that Washington would provide defense means for the Ukrainians.

But at the same time, he stressed that "the idea of ​​the United States using force unilaterally to confront Russia if it invades Ukraine, is out of the question."

"We have a moral and legal duty to our NATO allies under Article V. It is a sacred duty, and that duty does not include Ukraine," he said.

In the same context, the White House said that the US administration is holding meetings at the highest levels with Russia on Ukraine, and "our goal is to resolve the crisis diplomatically."

'constructive' conversations

On the other hand, Russian President Vladimir Putin said that his talks with his American counterpart Joe Biden were open and constructive, and that there is a possibility to continue the dialogue after the last contact, noting that his country will send its proposals to the American side within a week.

The Russian President said that the extension of the North Atlantic Treaty Organization (NATO) towards the Russian borders is unacceptable, and expressed his belief that Ukraine will deploy additional weapons if it joins NATO.

Putin considered that NATO is following a clear confrontational approach with Russia, stressing that his country does not seek confrontation, and added that he agreed with Biden to talk in detail in the future on the issue of security.

He pointed out the need for international security, and this applies to everyone, on an equal footing, as he put it.

Crowds and fears

These statements come amid Ukrainian and Western reports of a huge Russian military build-up on Ukraine's borders, and also in light of high tension between Russia and NATO, with Ukraine and other countries in the Baltic region seeking to join the alliance.

Ukraine confirmed that Russia has amassed 94,000 troops on its borders, and expected to attack it in late January.

But Russia denied having any intention of attacking Ukraine, and responded by accusing Kiev of planning a military operation in the Donbass region (eastern Ukraine), which has been witnessing a conflict since 2015 between Ukrainian forces and militias loyal to Moscow.

Kremlin spokesman Dmitry Peskov said that representatives of Russia and the United States will soon begin - pragmatically - discussing strategic stability issues raised at the summit on Tuesday.

Peskov explained that the two presidents agreed to appoint their representatives to discuss issues of security and strategic stability in the European continent as soon as possible.

Peskov noted that the two leaders also agreed on the possibility of further contacts, after the meeting of representatives of Russia and the United States, explaining that so far it is difficult to set a date for this.

He added that Putin and Biden did not discuss the issue of the "Nord Stream-2" line in the last call.

Threatening harsh punishments

The White House had stated that Biden had told Putin that Washington and its allies would respond with severe economic sanctions if Moscow escalated militarily.

Reuters quoted US officials as saying that they had informed Congress of their understanding with Germany to close the Nord Stream pipeline to transport Russian gas if Russia invaded Ukraine.

As for Ukrainian President Volodymyr Zelensky, today, Wednesday, he confirmed that the call between US President Biden and his Russian counterpart, Putin, was "positive."

Speaking to reporters alongside Croatian Prime Minister Andrej Plenkovic, Zelensky said he would comment "in detail" on the call on Thursday after speaking with Biden.

"I believe that Ukraine's victory is due to the fact that the United States has always supported Ukraine, our sovereignty and our independence," he said.

"But most importantly, we now have a real and personal response from President Biden, as well as his personal role in resolving the conflict," he added.

Zelensky: US President Biden's call with his Russian counterpart Putin was "positive" (Reuters)

Dialogue and partnership

This comes as Ukrainian Foreign Minister Dmitro Kuleba leaves for Britain today, Wednesday, to participate in the preparatory meeting for the partnership dialogue between Ukraine and the United Kingdom.

During his visit, Kuleba will raise the issue of strengthening support for Ukraine, against the backdrop of what he called Russia's aggressive actions.

In this context, he said that he was confident that Putin had heard from Biden very clear and strong signals regarding the escalation of Russia.

Kuleba indicated that the priority is to compel Moscow to reduce the escalation, and added in statements to Reuters that his country appreciates the decisive diplomatic participation of the United States in efforts to bring Russia back to the negotiating table.

He indicated that the Ukrainian and American presidents will discuss further coordination to deter Russia and revive peace talks within the "Normandy formula."

These developments come at a time when France has warned Russia of "strategic and huge consequences" if it hits Ukraine.

The French Foreign Ministry said on Wednesday that "firm messages have been conveyed to Russia about the strategic and huge consequences (that will result from) a new attack on Ukraine's territorial integrity."