'The world's fault': Ukrainian President Volodymyr Zelenskyy speaks out amid Russian assault

The situation in Ukraine is so serious that President Volodymyr Zelenskyy had to cancel a planned trip to Spain and come straight to Kharkiv -- the country's second largest city, which is again in real danger from the Russian advance.

With exclusive access, ABC News joined Zelenskyy on a tour of a hospital in the city, with Zelenskyy, where he met soldiers injured in the northern defense, and presented them with medals of valor.

"It's really important for me to be here," he told us, as we walked the corridors.

In each ward, he stopped as an officer read out the names of each injured soldier. He approached each bed and presented them with a medal. But this was a very rushed visit. The president's safety is always a concern, but this trip to Kharkiv was a risk and his team moved quickly around the building.

"The situation is very serious," Zelenskyy said. "We cannot afford to lose Kharkiv."

As he stood near the injured soldiers, he was very clear that the delay in U.S. aid has had a direct impact on the war, and the situation along the northeastern border. Hundreds had lost their lives or been wounded in the last few days, he said. Many were soldiers from this region, so it was important for him to be there, supporting them, he said.

Is it America's fault, we asked him, what's happening now in Kharkiv?

"It's the world's fault," he replied. "They gave the opportunity for Putin to occupy. But now the world can help."

He's always careful not to criticize the U.S. But this was a slightly more frank Zelenskyy than we usually see.

We asked how he felt the visit this week by Secretary of State Antony Blinken had gone. The U.S.'s top diplomat on Wednesday announced an additional $2 billion in aid, adding to the $60 billion promised in late April. Zelenskyy paused. I could sense his frustration.

"Dialogue is good," he said. "But we need help now."

There's a sense here, near the brutal fighting on the front line, that the visit wasn't much more than a show of support.

"All we need are two Patriot systems," he said. "Russia will not be able to occupy Kharkiv if we have those."

I told him many Americans are worried about how much money is being spent on Ukraine. And in this election year it's going to be an issue that American voters pay attention to.

"That money is not given to Ukraine," he said. "It's money spent in American factories, creating American jobs... And we are not just fighting for our freedom. If not Ukraine, it would be another country."

After the president left, we returned to some of the soldiers he'd visited.

Maxim, who nearly died in Vovchansk on Wednesday, had his leg raised with three huge metal pins keeping it straight. These are the men protecting Kharkiv. He didn't seem too bothered with his medal.

"It's an honor," he told me. "But I'd prefer to award this to the men who saved my life."