US President Joe Biden welcomes the heads of NATO member states to Washington on Tuesday for an annual summit that gives the embattled Democrat an international stage to convince allies at home and abroad he can still lead.

Biden, 81, has vowed to press on in his race against Republican Donald Trump, 78, despite concern from Democrats on Capitol Hill and donors that he will lose the Nov. 5 election after a halting debate performance on June 27.

Biden made restoring the United States' traditional alliances abroad to counter the threat of autocracies the centerpiece of his foreign policy after Trump challenged allies as part of an "America First" approach. Who wins in November could have a substantial impact on NATO's and Europe's future.

Trump has suggested that, given a second term, he would not defend NATO members that did not meet the alliance's defense spending target of 2% of their respective GDP if they came under military attack. He has also questioned the amount of aid given to Ukraine in its battle against Russia's invasion.

Aides said Biden's opening speech expected at 5 p.m. Eastern time (2100 GMT) will highlight what his administration sees as a key accomplishment: a stronger and more united NATO, under Washington's leadership, with more members and a resolve to meet their collective security needs.

That brings, they say, tangible results for American voters: a safer country, with a strong international economic position, more alliances and power abroad, and less at risk of conflict with its adversaries.

The mere presence of leaders from NATO and beyond shows Biden's power to assemble coalitions and inspire confidence, Kirby said, arguments that Trump and many of his Republican allies reject.

"Republicans, of course, celebrate the peace and prosperity that NATO has secured and will continue to stand by our partners as we prevent needless wars," said U.S. House of Representatives Speaker Mike Johnson, a top Republican and Trump ally, on Monday. "But we also believe that NATO needs to be doing more."