Ukraine will stop Putin, Biden tells NATO

US President Joe Biden pledged to forcefully defend Ukraine against Russia's invasion at the NATO summit in Washington on Tuesday, using the global stage to try to show allies at home and abroad that he can still lead.

Biden, 81, has endured 12 days of withering questions about his fitness for office as some of his fellow Democrats on Capitol Hill and campaign donors fear that he will lose the November 5 election after a halting debate performance on June 27.

"(Vladimir) Putin wants nothing less, nothing less, than Ukraine's total subjugation...and to wipe Ukraine off the map," Biden said in his welcome to NATO member states to the summit, referring to the Russian president. "Ukraine can and will stop Putin."

Biden spoke off of a teleprompter with a strong and confident voice and largely avoided the verbal flubs and signs of confusion that marked his debate performance.

He was framed by the gilded walls of the federal hall where the treaty creating NATO was signed, his speech bookended by stirring musical performances by the US Marine Corp band.

"Today NATO is stronger than it's ever been in its history," he said.

Biden closed his remarks by surprising NATO Secretary-General Jens Stoltenberg with the Presidential Medal of Freedom, clasping the highest US civilian award around the Norwegian politician's neck and crediting him with reviving the 32-member alliance.

The centerpiece of the NATO summit is set to be new commitments of military and humanitarian aid to Ukraine. US Secretary of State Antony Blinken said the summit would "further strengthen" the war-torn country's path to NATO membership.

Biden and the leaders of Germany, Italy, the Netherlands and Romania issued a joint statement with Ukrainian President Volodymyr Zelenskiy announcing the delivery of five additional Patriot and other strategic air defense systems to protect Ukrainian cities, civilians and soldiers.

They said additional strategic air defense systems would be announced this year.

Ukraine ultimately wants to join NATO to ward against further future attacks by Russia but candidates have to be approved by all of the alliance's members, some of which are wary of provoking a direct conflict with Russia.

Some members want the alliance to make clear Ukraine is moving toward NATO "irreversibly" and are keen for language in a summit statement beyond the alliance's pledge last year that "Ukraine's future is in NATO."