After Russian President Vladimir Putin put Russia’s nuclear deterrent forces on a state of heightened alert this weekend, a White House official confirms the U.S. has not changed its own alert level.

"We are assessing President Putin’s directive and at this time see no reason to change our own alert levels," a White House official confirmed to ABC News.

"We think provocative rhetoric regarding nuclear weapons is dangerous, adds to the risk of miscalculation, should be avoided, and we will not indulge in it," the official added.

The official also noted that, as recently as June, when President Joe Biden met Putin face-to-face in Geneva, the two leaders affirmed nuclear war is tantamount to mutually assured destruction.

The leaders said in a joint statement in June, "Today, we reaffirm the principle that a nuclear war cannot be won and must never be fought."

-ABC News' Sarah Kolinovsky

Russia’s central bank on Monday raised its key interest rate to 20% from 9.5% in an apparent effort to slow the fallout from severe international sanctions. 

The rate hike came as the Russian ruble tumbled, trading down as much as 30% against the U.S. dollar on Monday, according to Bloomberg. The currency traded about 17% lower midday in Moscow.

The Russian stock market reportedly closed for the day. 

-ABC News’ Zunaira Zaki

More than 500,000 people have fled Ukraine since the Russian invasion began on Thursday, the U.N. Refugee Agency said on Monday.

More than half have crossed the border into Poland, the agency said. Filippo Grandi, the U.N. high commissioner for refugees, had said on Sunday that 368,000 people had fled to neighboring countries.

-ABC News’ Zoe Magee

The Ukrainian delegation sent for talks with Russia arrived Monday morning at the Belarus-Ukraine border, where the meeting will be held.

Ukraine has said the key issue for the talks is an immediate ceasefire and the withdrawal of Russian troops.

Russia has signalled it wants to discuss Ukraine adopting “neutral status.” 

The head of Russia’s delegation has said the two sides will meet within about an hour. They are meeting on the Pripyat River, north of Chernobyl.

The Ukrainian delegation includes the Minister of Defense Oleksiy Reznikov, the head of Zelenskyy’s parliamentary party, as well as advisors to the president and MPs.

Russia’s delegation includes officials from the Foreign and Defense ministries, and the presidential administration.

The talks were agreed to on Sunday in a call between Ukraine’s President Volodymyr Zelenskyy and Belarus’ leader Alexander Lukashenko.

Fighting continued throughout the night, as Russia attempted to advance and bombarded Ukrainian forces.

-ABC News’ Patrick Reevell and Julia Drozd

Homeland Security to take lead response to Russia-related impacts in US

The Department of Homeland Security has been tasked "to coordinate domestic preparedness and response efforts related to the current Russia-Ukraine crisis," the agency announced Thursday evening.

The agency said there are no current threats to the U.S. 

Homeland Security said it established a unified group "preparing for and responding to possible threats to the homeland; develop and pursue strategic objectives and priorities; and coordinate with federal, state, local, tribal, and territorial officials, as well as representatives of the private sector and nongovernmental entities in support of these objectives and priorities."

-ABC News' Luke Barr