AMNA NAWAZ: The tense alliance between Ukrainian President Zelenskyy and President Trump is nearing a new low point tonight.

After days of bitter back-and-forth between the two leaders, Ukraine has resumed strikes on Russian energy targets following three days of Ukrainian cease-fire.

The president had demanded an energy cease-fire this past Sunday between the two.

Russia never stopped its attacks.

Lisa Desjardins begins our coverage.

LISA DESJARDINS: In Ukraine's capital city today, Russian strikes reverberate in broad daylight, that after Ukrainian officials say Russia launched a large-scale overnight attack, more than 850 drones.

But Russia too is burning.

The Associated Press reports Ukraine hit this oil refinery.

VOLODYMYR ZELENSKYY, Ukrainian President: Three days, we didn't attack any energy, diesel and et cetera systems of Russia, and three days they attack us.

LISA DESJARDINS: Late yesterday, Ukrainian President Volodymyr Zelenskyy told The Financial Times that Russia never abided by the cease-fire announced by Trump.

Zelenskyy criticized the U.S.

for limiting intelligence resources like Starlink.

He was blunt.

His patience is gone.

QUESTION: If they keep doing this, how much longer will you maintain the stoppage of attacks on Russian refineries?

VOLODYMYR ZELENSKYY: That's it.

Block is out.

LISA DESJARDINS: His candor continued when asked about Trump's relationship with Russian President Vladimir Putin and their deal on diesel.

VOLODYMYR ZELENSKYY: He speaks about it, I mean, openly and loudly that he loves such people and he respects such people, because, for him, I don't know, people who can be leaders 20 years, 30 years, 40 years, it's means they're very strong because they -- you can, I mean, hold the power.

How it can be when some people are surviving, fighting, dying, you make some business with the guys with such aggression?

LISA DESJARDINS: For his part, Putin accused Ukraine of violating the truce.

VLADIMIR PUTIN, Russian President (through translator): They made a first step.

We started to respond by striking at energy facilities, which they are now squealing about.

It was them who started it.

They should have thought properly about consequences.

LISA DESJARDINS: And Russia's foreign minister said Zelenskyy's comments point to a deepening rift between Kyiv and Washington.

SERGEY LAVROV, Russian Foreign Minister (through translator): The fact that this is such a direct and indeed crude challenge to President Trump is, in my view, something everyone already understands.

LISA DESJARDINS: Zelenskyy spent his day at an E.U.

summit in Brussels focused on support from his European allies.

KAJA KALLAS, High Representative, European Union: We definitely have different approach to this war.

We see that we have to pressure the aggressor to stop the war, not the victim to surrender.

Squeezing Ukraine is not the right approach.

LISA DESJARDINS: The talks come as the entire region grows more war-weary.

Two cargo ships were set ablaze today in Romanian waters in the Black Sea.

Seven crew members are missing.

NICUSOR DAN, President of Romania (through translator): There are attempts by Russia to destabilize societies and to reduce support for Ukraine.

And our response is, we continue to support Ukraine.

LISA DESJARDINS: European leaders also rejected Trump's push to control and release frozen Russian assets, he said, as a bargaining ship.

FRIEDRICH MERZ, German Chancellor (through translator): These are assets that are frozen in Europe.

And they should remain frozen in Europe.

This is our business.

And we decide on it.

LISA DESJARDINS: And, as world leaders talk, the war grinds on, on the ground.

For the "PBS News Hour," I'm Lisa Desjardins.