Former Secretary of State James Baker told a U.S. Senate hearing that Donald Trump's foreign policy proposals would make the world a less stable place on Thursday, just as the Republican presidential candidate met with party congressional leaders.

Under questioning from Republican Sen. Marco Rubio, a former Trump rival in the presidential race, Baker said the world "would be far less stable" with a weaker NATO or if more countries had nuclear weapons as has been proposed by Trump.

"We've a got a lot of problems today, but we'd have a hell of a lot more if that were the case," Baker told a Senate Foreign Relations Committee hearing, adding that U.S. commitments around the world "promote U.S. security."