United States President Joe Biden has forcefully pledged to defend Ukraine against Russia’s invasion, announcing dozens of new air defence systems for Kyiv, as he welcomed NATO leaders for a summit in Washington, DC.

The address on Tuesday was Biden’s highest-profile policy speech since a halting performance in a debate on June 27 that raised questions about his fitness for office as well as fears that he may lose the November 5 election to his predecessor and NATO sceptic, Donald Trump.

Speaking off a teleprompter, his voice confident and strong, Biden declared that NATO was “stronger than it’s ever been in its history”. And that is a good thing, he said, “because this moment in history calls for our collective strength”.

“Autocrats want to overturn the global order” and “terrorist groups” continue to plot “evil schemes”, Biden said, while in Europe, Russian President Vladimir Putin seeks to wipe “Ukraine off the map”.

“But make no mistake, Ukraine can and will stop Putin,” the US leader said, “especially with our full, collective support. And they have our full support.”

Biden, who has so far rebuffed calls to withdraw from the presidential race, has made restoring traditional alliances abroad the centrepiece of his foreign policy. On the campaign trail, he has sought to spotlight his commitment to NATO while making the case to voters that Trump would turn his back on the alliance if he were to return to the White House.

The US president announced major steps Washington and other NATO countries are taking to beef up Ukraine’s overwhelmed air defences. He said the US, Germany, the Netherlands, Romania and Italy would provide Ukraine with the equipment for five additional strategic air defence systems.

These include four additional Patriot batteries and a SAMP/T defence system.

“In the coming months, the United States and our partners intend to provide Ukraine with dozens of additional tactical air defence systems,” he added. “All told, Ukraine will receive hundreds of additional interceptors over the next year, helping protect Ukrainian cities against Russian missiles and Ukrainian troops facing air attacks on the front lines.”

European anxiety over Trump

NATO, which is celebrating its 75th anniversary, has found a new purpose in opposing Putin’s Ukraine invasion and the grinding war will dominate private conversations between the leaders of the countries.

But with less than four months to go before the US presidential election, Biden’s political travails, too, loom large.

Robert Hunter, a former US ambassador to NATO, told Al Jazeera that “there’s an awful” lot of worry among NATO leaders about a possible Trump return. “They would really like anybody but Mr Trump to be president,” he said.

Trump has repeatedly criticised fellow NATO members who failed to meet an agreed-upon goal of spending at least 2 percent of gross domestic product (GDP) on defence, warning in February that he “would encourage” the Russians “to do whatever the hell they want” to countries that do not meet those targets.

Hunter said it was unclear if Biden’s speech was enough to calm European anxiety about his staying power.

“Biden was clearly well-rehearsed, he read it well, the substance was good he had a lot of energy. This is a kind of leader one would want within the alliance, but whether that’s gonna be enough to change minds – I have no idea,” said Hunter. “He’s got another day and a half he’s got to get through. Some of it unscripted, as today was very tightly scripted.”

Meanwhile, the Reuters news agency quoted a European diplomat as saying the damage from Biden’s debate performance was hard to erase.

“We don’t see how he can come back after the debate,” the diplomat said, dismissing Tuesday’s speech as evidence of Biden’s endurance because it was scripted. “I can’t imagine him being at the helm of the US and NATO for four more years.”

The Associated Press news agency also quoted several US officials as saying that while the president displayed a strong grasp of the broader issues such as Russia’s invasion of Ukraine, he has appeared confused at times on specific and incremental actions that countries or groups may take when it comes to these conflicts.

But the officials said there was not – at least not yet – a crisis in confidence over Biden’s general mental state.

German Chancellor Olaf Scholz told reporters on Tuesday before departing Berlin for the summit that he did not have any concerns about Biden’s health. “From the many conversations I have had with the American president, I know that he has prepared this summit very well and very precisely together with us,” Scholz said.

The gathering of the leaders from the 32 NATO countries – plus Pacific partners Australia, Japan, New Zealand and South Korea, as well as Ukraine – is expected to be one of Biden’s last appearances at an international forum before the US election.

He is expected to meet Ukraine’s President Volodymyr Zelenskyy on Thursday and hold a rare solo news conference, partly aimed at quieting concerns over his fitness for office.

Zelenskyy, meanwhile, said he would fight for “additional security guarantees” at the NATO summit, including “weapons and finances and political support”.

Ukraine ultimately wants to join NATO to ward against 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 Moscow. Some members want the alliance to make clear Ukraine is moving towards 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”.

Media reports say NATO leaders will once again stop short of offering a guaranteed timeline for Ukraine to enter the alliance. Instead, they will present Zelenskyy with what officials are calling a “bridge to membership” that is supposed to lay out specific tasks, including governmental, economic and rule-of-law reforms, that Ukraine must fulfil to join.

But meeting those steps will not be enough. The alliance has previously said it would not admit a new member until the conflict with Russia is resolved.

For his part, Zelenskyy, addressing US political leaders on Tuesday, urged the world not to wait for the outcome of the country’s election to aid his country.

“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,” Zelenskyy said at the Ronald Reagan Institute.

“It is time to step out of the shadows, to make strong decisions … to act and not to wait for November or any other month,” he said.