Russia-Ukraine updates: US to ban Russian carriers from its airspace

In the first response to Russia raising the alert status of its strategic nuclear force, a senior U.S. defense official described the move as an "escalatory one."

The official pointed out that Russia has never been under threat by NATO or Ukraine and warned that Russia's heightened alert status is "clearly potentially putting at play forces that could if there's a miscalculation make things much, much more dangerous."

"We believe that this is not only an unnecessary step for him (Russian President Vladimir Putin) to take but an escalatory one," the official said. "Russia has never been under threat by NATO. Ukraine did not threaten Russia."

The official would not discuss the status of the U.S. nuclear force, saying "we do not talk about ... specifics of our strategic deterrent posture."

"I would just tell you that we remain confident in our ability to defend ourselves and our allies and our partners, and that includes in the strategic deterrent realm," the official said.

-ABC News' Luis Martinez

Ukraine has agreed to send a delegation to meet with Russian negotiators for talks at the border between Belarus and Ukraine, according to a spokesman for Ukraine’s president’s office.

President Volodymyr Zelenskyy agreed to the step during a phone call with Belarus’ authoritarian leader Alexander Lukashenko, the spokesman said.

The spokesman said the two sides have agreed to meet at the Pripyat river on the border, north of Chernobyl. That area is currently under Russian military control.

Russia earlier sent a delegation to the city of Gomel in southern Belarus to “be ready” for talks but Ukraine refused to hold them in Belarus since it is actively taking part in the invasion.

The Russian delegation includes officials from Russia’s foreign and defense ministries as well as the presidential administration.

-ABC News’ Patrick Reevell

Russian President Vladimir Putin has ordered his military to put Russia's strategic deterrence forces in a state of heightened readiness, saying it is a response to what he called "aggressive statements" from NATO countries.

In a televised meeting, Putin ordered his defense minister and chief of general staff to move Russia's forces, including the nuclear triad, into a "special regime of combat duty,"

The announcement appears to be intended as rattling Russia's nuclear saber at Western countries as they send large numbers of weapons to Ukraine and sanction Russia.

"Senior officials of the leading NATO countries allow aggressive statements against our country, therefore I order the minister of Defense and the chief of the General Staff to transfer the deterrence forces of the Russian army to a special combat duty regime," Putin said during a meeting with Defense Minister Sergei Shoigu and Chief of the General Staff of the Russian Armed Forces Valery Gerasimov.

-ABC News' Patrick Reevell and Tanya Stukalova

The United States will provide $54 million in humanitarian aid to help Ukrainians, Secretary of State Antony Blinken said on Sunday. 

“This assistance enables humanitarian organizations to support citizens of Ukraine already in need and those newly affected by Russia's unprovoked and unjustified attack,” he said on Twitter. 

With the new funding, the U.S. has provided about $405 million in humanitarian aid to Ukraine since 2014, Ned Price, spokesperson for the State Department, said on Twitter.