Outlining his vision for a shake-up in the world order, Trump also said he would "love" to have Russia back in the G7, from which it was suspended in 2014 after Moscow annexed Ukraine's Crimea peninsula.

"I think it was a mistake to throw him out," Trump said, referring to Russian President Vladimir Putin.

Trump -- who sees himself in his second term as a global peacemaker -- also said he would consider a summit with Putin and China's Xi Jinping "when things calm down."

"When we straighten it all out, then I want one of the first meetings I have is with President Xi of China, President Putin of Russia. And I want to say, let's cut our military budget in half."

"There's no reason for us to be building brand new nuclear weapons," he added.

Trump made his comments at the White House after he inked plans for sweeping "reciprocal tariffs" that could hit both allies and competitors.

In 2014, Russia was suspended from what was then the G8 after it annexed Crimea and sanctions were imposed on Moscow.

In his first term, Trump also called for Russia to be readmitted, but he found little support among other Western countries.

Trump revealed Wednesday he expected to meet Putin separately for Ukraine peace talks, in a sudden thaw in relations.

In their first confirmed contact since Trump's return to the White House, the US president said he had held a "highly productive" conversation with his Russian counterpart who ordered the bloody 2022 invasion of Ukraine.