Trump made quickly stopping the war one of his diplomatic priorities, and he has increasingly expressed frustration about Russian President Vladimir Putin's unbudging stance on US-led peace efforts.
Trump has long boasted of his friendly relationship with Putin, and after taking office in January repeatedly said Russia was more willing than Ukraine to reach a peace deal.
Trump also accused Ukrainian President Volodymyr Zelenskiy of prolonging the war and called him a "dictator without elections".
But Russia's relentless onslaught against civilian areas of Ukraine wore down Trump's patience.
"I am very disappointed with President Putin, I thought he was somebody that meant what he said," Trump said late on Sunday.
"He'll talk so beautifully and then he'll bomb people at night. We don't like that."
Russia has pounded Ukrainian cities with hundreds of drones and cruise and ballistic missiles that Ukraine's air defences are struggling to counter.
June brought the highest monthly civilian casualties of the past three years, with 232 people killed and 1343 wounded, the UN human rights mission in Ukraine said.
Russia launched 10 times more drones and missiles in June than in the same month in 2024, it said.
At the same time, Russia's bigger army is making a new effort to drive back Ukrainian defenders on parts of the 1000km front line.
Trump confirmed the US was sending Ukraine more badly needed Patriot air defence missiles and the European Union would pay the US for the "various pieces of very sophisticated" weaponry.
While the EU is not allowed under its treaties to buy weapons, EU member countries can and are, just as NATO member countries are buying and sending weapons.
A top ally of Trump, Republican senator Lindsey Graham, said on Sunday the conflict was nearing an inflection point as Trump showed growing interest in helping Ukraine fight back against Russia's full-scale invasion.
It's a cause that Trump had previously dismissed as being a waste of US taxpayer money.
"In the coming days, you'll see weapons flowing at a record level to help Ukraine defend themselves," Graham said on CBS's Face the Nation.
He added: "And you just watch, in the coming days and weeks, there's going to be a massive effort to get Putin to the table."
Kirill Dmitriev, Putin's envoy for international investment who took part in talks with US officials in Saudi Arabia in February, dismissed what he said were efforts to drive a wedge between Moscow and Washington.
"Constructive dialogue between Russia and the United States is more effective than doomed-to-fail attempts at pressure," Dmitriev posted on Telegram.
NATO Secretary-General Mark Rutte was due in Washington on Monday and Tuesday to hold talks with Trump, Defense Secretary Pete Hegseth and Secretary of State Marco Rubio, as well as members of Congress.
Talks during Kellogg's visit to Kyiv would cover "defence, strengthening security, weapons, sanctions, protection of our people and enhancing cooperation between Ukraine and the United States", said the head of Ukraine's presidential office, Andrii Yermak.
Russian troops conducted a combined aerial strike at Shostka, in the northern Sumy region of Ukraine, using glide bombs and drones early on Monday morning, killing two people, the regional prosecutor's office said.
Overnight, Russia fired four S-300/400 missiles and 136 Shahed and decoy drones at Ukraine, the air force said.
It said 61 drones were intercepted and 47 more were either jammed or lost from radars mid-flight.
Russian said its air defences downed 11 Ukrainian drones over border region, annexed Crimea and the Black Sea.
