Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

The United States will provide Ukraine with $322 million in new aid and some diplomats will return to the war-torn country, U.S. Secretary of State Antony Blinken and U.S. Defense Secretary Lloyd Austin told Ukrainian President Volodymyr Zelenskyy in Kyiv on Sunday.

Blinken told Zelenskyy the U.S. would begin returning its diplomats to Ukraine this week, according to the senior State Dept. official. The U.S. will reopen offices in Lviv in western Ukraine, with diplomats traveling there from Poland each day, with the goal to "have our diplomats return to our embassy in Kyiv as soon as possible."

President Joe Biden will also formally nominate Bridget Brink, currently serving as U.S. ambassador to Slovakia, to serve as the U.S. ambassador to Ukraine, according to the senior State Dept. official.

Among the new assistance announced last week, the first of the new Howitzers have arrived in Ukraine, Austin told Zelenskyy, a senior defense official told ABC News.

-ABC News’ Conor Finnegan

An advisor to Ukrainian President Volodymyr Zelenskyy said that U.S. Secretary of State Antony Blinken and U.S. Defense Chief Lloyd Austin are meeting with Ukraine's leader on Sunday in Kyiv.

The adviser, Oleksii Arestovich, said in an interview on Ukrainian TV late Sunday that the talks are going on "right now."

-ABC News' Jason Volack

More than 2.9 million people have fled Ukraine and sought refuge in Poland since the Russian invasion began in February, the Polish Border Guard said on Sunday.

In recent days, however, the number of people crossing the border into Poland has fallen, while the number of refugees going back into Ukraine has risen, according to the border guard.

On Saturday, about 21,100 people entered Ukraine from Poland, while 15,100 fled to Poland from Ukraine, the agency said on Twitter.

Ukraine's losses, including destroyed homes and massive damage to the country's infrastructure, has topped $1 trillion since Russian forces invaded the country two months ago, according to Ukraine's top economic advisor.

Oleg Ustenko, economic adviser the Ukrainian president, announced the country's staggering losses in a televised address on Sunday.

"This is what was destroyed by the Russian invaders in our assets. It is clear that this figure literally increased every day ... the aggressor destroyed our infrastructure, destroyed the homes of our citizens, destroyed everything that could be destroyed by their own and air strikes, and simply by dropping bombs and everything they did," Ustenko said.

Ustenko said additional losses have come as a result of Ukraine's declining gross domestic product.

"It is this figure that we must focus on," Ustenko said. "It is this figure that should be compensated by the Russian Federation immediately after our victory."