Blinken promises US arms on the way, says allies won't leave Ukraine's side

Secretary of State Antony Blinken, during an unannounced visit to Ukraine on Tuesday, promised the U.S. will quickly deliver badly needed arms, touting Washington and the West's alliances with Kyiv.

Blinken is the first senior U.S. official to visit since Congress, after months of dispute, in April passed and President Joe Biden signed a $60 billion aid package that includes artillery and other weapons systems vital to Ukraine's defense.

After meeting with President Volodymyr Zelenskyy, America's top diplomat told an audience of Ukrainians "you are not alone," but acknowledged that "delay" in approving new arms "left you vulnerable to Russian attacks."

Blinken's fifth trip to the country comes amid consistent shelling of Kharkiv, the country's second-largest city, as the Russians conduct an offensive in Ukraine's east.

Zelenskyy, who said "a tough period for the east of our country" is unfolding for Ukraine's armed forces, thanked the United States and allies for their military support.

"The decision of the package was crucial for us," Zelenskyy said.

It is still unclear how costly the delay was for Ukraine as the Russians threaten Kharkiv -- but the U.S. says it's rushing critical weapons to the frontlines.

A senior U.S. official said the American aid package focused "primarily on capabilities that can be delivered in the next 12 months," and that key systems like longer-range ATACMS missiles, which the U.S. acknowledged it dispatched to Ukraine for the first time in April, "are already on the frontlines."

The fighting in Kharkiv is intensifying, a Pentagon spokesperson said Monday, assessing "that Russia has launched an offensive in and around Kharkiv," where "cross-border fire [will] likely increase."

Vovchansk, a city in Kharkiv, has seen 7,000 people flee as the city is "almost destroyed," its top administrator said Tuesday. Russia has not taken the city but has penetrated on the outskirts, the local official said.

Zelensky said "air defense [is] the biggest deficit for us," adding his forces "really need" two batteries of U.S. Patriot missile systems in Kharkiv.

"Civilians and warriors -- everybody -- they are under Russian missiles," the Ukrainian president said.

The U.S. aid package appropriates munitions for the Patriot systems, but it doesn't fund new systems.

Blinken praised the Patriots as crucial security systems which "create umbrellas of safety," but he didn't say whether the U.S. will provide them.

The secretary echoed his Pentagon counterpart in promising the U.S. would work with allies -- and not act unilaterally -- to procure air defenses for Ukraine.

"I would caution us all in terms of making Patriot the silver bullet," Defense Secretary Lloyd Austin said on April 26. "I would say that it's going to be the integrated air and missile defense, as we said so many times before, that really turns the tide."

Blinken said he came to Kyiv to highlight "Ukraine's strategic success," including positive developments for its democracy, industrial independence, and economic ties with the west -- all threads that will help it interlock with the U.S. and Europe, and "get closer to, and into, NATO."

A Ukraine that stands "strongly on its own feet," militarily and economically over the long term, is one that will sustain strong defenses against Russia, Blinken said. He said the U.S. and its allies were committed to seeing that happen.

The secretary of state said the boost should come "not after the war but right now," praising Ukraine's efforts to meet western standards ahead of a July NATO summit in Washington.

Ukrainians "have as much experience as any on Earth in fighting the wars to come," he said. "You have a lot to teach the alliance, and NATO will be more secure with your military by our side."

Ukraine's anti-corruption work is "absolutely critical" to potential NATO accession, Blinken said.

"Winning on the battlefield will prevent Ukraine from becoming part of Russia. Winning the war against corruption will keep Ukraine from becoming like Russia," he said.

Blinken conceded that the election-year standoff in Congress over the aid might leave Ukrainians "wondering whether you can count on America to sustain its commitment."

He made the case that the wide bipartisan vote by which the package eventually passed Congress "I think demonstrates you can."

ABC News' Shannon Crawford, Matt Seyler, and Will Gretzky contributed to this report.