Trump-Putin summit: Zelenskyy to travel to DC on Monday to meet with President Trump

Joining President Donald Trump at the summit are Defense Secretary Pete Hegseth as well as Gen. Dan Caine, the president's top military adviser, and Gen. Alexus Grynkewich, the top NATO and U.S. commander in Europe.

Grynkewich has been playing a lead role in orchestrating new military aid for Ukraine, including an initial aid package now totaling $1.5 billion.

Under the plan endorsed by Trump, five European allies -- the Netherlands, Norway, Denmark, Sweden and Germany -- have agreed to purchase air defense capabilities, missiles, artillery and ammunition from U.S. companies. The weapons would then be provided to Ukraine. A senior NATO military official said to expect "further significant announcements from other allies soon."

Officials said Grynkewich and Caine, who is chairman of the Joint Chiefs, will be on hand at the summit to provide Hegseth and the president military advice.

-ABC News' Anne Flaherty

President Donald Trump on Air Force One said the U.S., in conjunction with Europe, could "maybe" provide security guarantees to Ukraine. Security guarantees post-war are a key demand of Ukrainian President Volodymyr Zelenskyy.

“Maybe, along with Europe and other countries. Not in the form of NATO, because that's not going to, you know, there are certain things that aren't going to happen. But, yeah, along with Europe, there's a possibility of that," Trump said.

-ABC News' Fritz Farrow

President Donald Trump told reporters on the flight to Alaska that there would be "economically severe" consequences for Putin if he does not appear interested in a peace deal.

"Economically severe. Yes, it will be very severe. I'm not doing this for my health. OK? I don't need it. I'd like to focus on our country, but I'm doing this to save a lot of lives. Yeah, very severe," Trump said.

Trump had set an Aug. 8 deadline for Putin to agree to a ceasefire or face secondary sanctions, but the deadline came without any new sanction announcements by the administration. Instead, that was the day Trump announced he would be meeting with Putin face-to-face on U.S. soil.

President Trump gaggled with reporters aboard Air Force One on his nearly seven-hour flight to Alaska.

Trump told ABC News Senior Political Correspondent Rachel Scott that land swaps will be discussed, but the decision is Ukraine's to make.

"They'll be discussed, but I've got to let Ukraine make that decision, and I think they'll make a proper decision. But I'm not here to negotiate for Ukraine. I'm here to get them at a table. And I think you have two sides. Look, Vladimir Putin wanted to take all of Ukraine. If I wasn't president, he would, right now, be taking all of Ukraine, but he's not going to do it," Trump said.

-ABC News' Fritz Farrow