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

Amid a three-year vacancy and with Ukraine in the grips of a brutal war, the U.S. Senate took its first major step towards confirming an American ambassador to Ukraine on Tuesday with a hearing in its Foreign Relations Committee for President Joe Biden's nominee, Bridget Brink.

Brink -- a veteran diplomat with 25 years of experience and the current U.S. ambassador to Slovakia -- acknowledged the great difficulties that would come with the post but said it would be the "honor of a lifetime."

"We face the biggest threat to peace and security in Europe in decades," she said during her opening statements. "If confirmed, I pledge to work with you to continue our commitment to a sovereign, democratic and independent Ukraine -- free to choose its own future."

Brink has bipartisan support and her path to confirmation appears to be a smooth one, though Sen. Jim Risch (R-Idaho), the ranking member of the committee, foretold "a lot scrutiny from Washington" when it comes to moving the U.S. embassy back to Kyiv and "helping to shepherd U.S. military, humanitarian and financial aid in the right places."

"I think it's really important for us to be there in person and present," Brink responded when questioned on plans to reopen the embassy in Kyiv. "I don't know exactly how fast we will be able to do this process, but I know we are trying to do it as fast as possible and it is certainly my hope and plan, if confirmed, to be able to start my mission in Kyiv."

She later added: "It's necessary for us to be there on the ground."

The nominee was also asked about the need for the aid package currently working its way through Congress.

"It is incredibly important that the supplemental move fast," Brink said. "The needs are large."

Brink also promised to work to assist Ukraine in holding Russia accountable for alleged war crimes.

"We are going to use every tool at our disposal," she said. "I can tell you it's a personal priority of mine."

-ABC News' Shannon Crawford

The House will vote on a new roughly $40 billion Ukraine aid package Tuesday night, House Speaker Nancy Pelosi announced.

The request includes funding for "critically needed resources, including military aid, support for the Ukrainian economy, and humanitarian assistance for food security to address the worldwide hunger crisis."

The White House had initially requested $33 billion in assistance for Ukraine, but congressional leaders decided to tack on an additional $7 billion for more military and humanitarian assistance.

"This package, which builds on the robust support already secured by Congress, will be pivotal in helping Ukraine defend not only its nation but democracy for the world. Time is of the essence – and we cannot afford to wait," Pelosi said in a letter to colleagues. "With this aid package, America sends a resounding message to the world of our unwavering determination to stand with the courageous people of Ukraine until victory is won."

The bill is expected to pass in the House, after which it would head to the Senate.

-ABC News' Mariam Khan

President Joe Biden will host House Speaker Nancy Pelosi and other members of Congress in the Situation Room on Tuesday afternoon to discuss the lawmakers' recent trip to Ukraine, according to White House press secretary Jen Psaki.

Biden previously spoke with Pelosi over the phone about her trip but wanted a more thorough discussion in person, Psaki said.

Expected to attend are: Rep. Jim McGovern, D-Mass.; Rep. Gregory Meeks, D-NY; Rep. Adam Schiff, D-Calif.; Rep. Barbara Lee, D-Calif.; Rep. Bill Keating, D-Mass.; and Rep. Jason Crow, D-Colo.

-ABC News' Ben Gittleson and Mariam Khan

Russian President Vladimir Putin "is preparing for prolonged conflict in Ukraine during which he still intends to achieve goals beyond the Donbas," according to Director of National Intelligence Avril Haines.

"The next month or two of fighting will be significant as the Russians attempt to reinvigorate their efforts. But even if they are successful, we are not confident that the fight in the Donbas will effectively end the war," Haines told senators at an Armed Services Committee hearing Tuesday.

For now, Putin's goal is to take control of the Donetsk and Luhansk oblasts and encircle Ukrainian forces from the north and south of the Donbas "in order to crush the most capable and well-equipped Ukrainian forces who are fighting to hold the line in the East," Haines said.

Putin also hopes to "consolidate control of the land bridge Russia has established from Crimea to the Donbas, occupy Kherson, and control the water source for Crimea," Haines said. The U.S. sees indications his military wants to extend that land bridge to Transnistria in Moldova, she added.

Haines said Russia might be capable of achieving "most" of those goals in the coming months. However, "We believe that they will not be able to extend control over a land bridge that stretches to Transnistria and includes Odessa without launching some form of mobilization. And it is increasingly unlikely that they will be able to establish control over both oblasts and the buffer zone they desire in the coming weeks," she said.

Sanctions from the West are having a "pretty significant" impact on Russia, according to Haines.

"Among the indicators that one might look at are, for example, the fact that we're seeing close to about, we predict, approximately 20% inflation in Russia; that we expect that their GDP will fall about 10%, possibly even more over the course of the year," she said.

The fighting itself has also worn on Russia's capabilities.

"The ground combat forces have been degraded considerably. It's going to take them years ... to rebuild that," she said.

But that could drive Putin to other means of exerting force. Haines said, "They may rely more on things like cyber, nuclear, precision, etc. … Putin would probably only authorize the use of nuclear weapons if he perceived an existential threat to the Russian state or regime."

Haines warned, "The current trend increases the likelihood that President Putin will turn to more drastic means, including imposing martial law, reorienting industrial production, or potentially escalatory military actions to free up the resources needed to achieve his objectives as the conflict drags on, or if he perceives Russia is losing in Ukraine."

"The most likely flashpoints for escalation in the coming weeks are around increasing Russian attempts to interdict Western security assistance, retaliation for Western economic sanctions or threats to the regime at home. We believe that Moscow continues to use nuclear rhetoric to deter the United States and the West from increasing lethal aid to Ukraine and to respond to public comments that the U.S. and NATO allies that suggest expanded Western goals in the conflict," she said. "If Putin perceives that the United States is ignoring his threats, he may try to signal to Washington the heightened danger of its support to Ukraine by authorizing another large nuclear exercise involving a major dispersal of mobile intercontinental missiles, heavy bombers, strategic submarines."

-ABC News' Matt Seyler