As the relations between Washington and Moscow hit their lowest point in decades, President Joe Biden urged Russian President Vladimir Putin on Tuesday to de-escalate tensions at Ukraine's border and proposed a summit in the near future.

The move by Biden came after thousands of Russian troops gathered along the Ukrainian border. According to Business Insider, the White House said that Biden spoke with Putin on Tuesday and discussed several regional and global issues.

The President clarified to Putin that the U.S. would act firmly in defending its national interests in responding to Russia's actions like cyber intrusions and interference in the elections.

In a statement, Biden also emphasized the U.S.' unwavering commitment to the sovereignty and territorial integrity of Ukraine.

The President also voiced their concerns regarding the sudden military build-up in occupied Crimea and on Ukrainian borders and called on to Kremlin to ease the tensions.

Biden also reiterated his goal is to build a stable and predictable relationship with Russia that is aligned with the interests of the U.S. 

He then called for a summit meeting in a third country in the next few months to discuss the full scope of the issues faced by the U.S. and Russia.

Anthony Blinken, the U.S. Secretary of State, made similar remarks in his talks on Tuesday. Blinken was in Brussels for talks with the foreign minister of Ukraine and North Atlantic Treaty Organization (NATO) leaders.

Blinken mentioned during their talks that the U.S. stands firmly behind the sovereignty and territorial integrity of Ukraine. He also pointed out the importance of this U.S. support, especially that Russia is currently doing provocative action against Ukraine.

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Russia Pushes Back Against U.S. Warnings

During his interview on Sunday, Blinken warned Russia of the consequences that it might face if it acts recklessly or aggressively. On Tuesday, Russia pushed back against the U.S. warnings and criticism.

In a Reuters report, Russian Deputy Foreign Minister Sergei Ryabkov said that the U.S. is their adversary and does everything it can to undermine Russia's position on the world stage.

Ukraine has been fighting a war against Kremlin-backed separatists in the Donbas region for the last seven years. 

The country said Russia had amassed an estimated 80,000 troops in a total, with 40,000 in Crimea and 40,000 along the eastern border. 

The massive build-up of Russian troops along the border with Ukraine and in Crimea, which the Kremlin head unilaterally annexed in 2014, has raised the alarm across Europe. 

On Tuesday, NATO Secretary-General Jens Stoltenberg urged Russia to withdraw its troops from the border, CNBC reported.

He added that NATO stands with Ukraine, and Russia must end the military build-up, stop its provocation, and de-escalate the situation immediately. 

Stoltenberg noted that the military build-up represented Russian troops' largest massing since the illegal annexation of Crimea in 2014.

Even German Chancellor Angela Merkel demanded Putin in a phone call last week about reducing the troops' presence to de-escalate the situation.

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WATCH: Biden Proposes Summit With Putin - From Reuters