By Phil Stewart and Idrees Ali
WASHINGTON (Reuters) -Ukrainian President Volodymyr Zelenskiy said on Tuesday he could not predict what Donald Trump would do if he regains the U.S. presidency in November, but the whole world, including Russian leader Vladimir Putin, was awaiting the outcome of the ballot.
Zelenskiy, speaking in Washington as world leaders gather for a NATO summit, said he hoped Trump would not quit the 75-year-old NATO alliance and that the United States would keep supporting Ukraine in its defense against Russia's invasion.
"I don't know (him) very well," Zelenskiy said of Trump.
He said he had "good meetings" with him during Trump's first presidency but said that was before the Russian invasion in 2022.
"I can't tell you what he will do, if he will be the president of the United States. I don't know."
Trump, the presumptive Republican nominee for the U.S. presidential election in November, has frequently criticized the size of U.S. military support for Ukraine - some $60 billion since the invasion - and called Zelenskiy "the greatest salesman ever."
Two of his national security advisers have presented Trump with a plan to end U.S. military aid to Ukraine unless it opened talks with Russia to end the conflict.
Trump's dealings with Zelenskiy became the subject of his first impeachment as president by the U.S. House of Representatives in 2019. He was accused of pressing Zelenskiy to help smear Joe Biden in return for aid, but was acquitted by the Senate in 2020.
On policy toward NATO, Trump has said he would "encourage" Russia to do "whatever the hell they want" to any alliance member that did not spend enough on defense and he would not defend them. The NATO charter obliges members to come to the defense of those who are attacked.
Speaking in the wake of a Russia missile strike on the main children's hospital in Kyiv on Monday, Zelenskiy said those kind of attacks made "you want to kill Putin".
"It's so difficult to lose children. And of course you see these people, you see parents, and when their children are dying or dead, you want to kill Putin at this moment," Zelenskiy said.
Zelenskiy urged U.S. political leaders on Tuesday not to wait for the outcome of the U.S. election in November to move forcefully to aid his country and he called for fewer restrictions on the use of U.S. weaponry.
"Everyone is waiting for November. Americans are waiting for November, in Europe, Middle East, in the Pacific, the whole world is looking towards November and, truly speaking, Putin awaits November too," Zelenskiy said.
"It is time...to act and not to wait for November or any other month."
Earlier on Tuesday, President Joe Biden pledged to forcefully defend Ukraine at the NATO summit.
But Biden, 81, is reeling from 12 days of questions about his fitness for office as some of his fellow Democrats on Capitol Hill and campaign donors fear that he will lose the election after a halting debate performance on June 27.
Trump is leading Biden by 2.1 percentage points nationally, according to a polling average maintained by website FiveThirtyEight.
Asked about Putin's views of Biden and Trump, Zelenskiy said cautiously: "Biden and Trump are very different. But they are supportive (of) democracy. And that's why I think Putin will hate both of them."
Zelenskiy's choice of venue, the Ronald Reagan Institute, could be another sign of Ukraine's effort to reach out to Republicans.
Andrew Weiss at the Carnegie Endowment think tank said Kyiv has been trying to build "as many bridges to the Republican mainstream establishment as possible."
"There's a process underway in Kyiv of trying to think through the implications of a possible Trump return to the White House," Weiss said.
Zelenskiy was introduced by top U.S. Senate Republican Mitch McConnell, who lauded the Ukrainian leader and strongly supported greater assistance to Kyiv.
"They need the tools to defend themselves to impose costs on their aggressors and to negotiate from positions of strength," McConnell said.