Tensions between Russia and Ukraine are reaching new heights as talks to avert a Russian invasion failed over the weekend.

What happened? Several world leaders spoke to Russian Pres. Vladimir Putin over the weekend in an attempt to ease tensions.

130K+ Russian troops are currently stationed at the Ukrainian border, signaling an imminent invasion of Ukraine. (AP)

CNN reported in Nov. that Russian military presence on the border increased by "two-thirds" that month.

U.S. intelligence in Dec. found satellite images showing Russian plans to deploy 175K+ troops to the border. (CNN)

Putin has demanded that NATO deny Ukraine membership and roll back its presence in eastern Europe. (Vox)

Russia has already invaded Ukraine before: in 2014, it invaded and annexed Crimea. (CNN)

US Pres. Biden and French Pres. Macron both spoke with Putin over the weekend in an effort to prevent an invasion. (CNN)

Biden warned Putin that the US and its allies would impose "swift and severe costs" on Russia in the event of an invasion.

White House: "...while the US remains prepared to engage in diplomacy...we are equally prepared for other scenarios." (CNN)

Talks are ongoing: UN Secretary-General António Guterres spoke to Russian and Ukrainian officials on Mon.

German Chancellor Olaf Scholz is set to head to the region this week to defuse tensions and prevent an invasion. (WaPo)

Scholz: "[This trip is] about how we can find a way to ensure peace in Europe." (Guardian)

US officials have warned that a Russian invasion of Ukraine could happen as soon as this week. (NYT)

The US has closed its embassy in Kyiv, Ukraine's capital, in anticipation of an imminent invasion. (AP)

What's next? Well, experts say that an attack could come as early as Wed. if talks fail. (AP)