Russia-Ukraine updates: US sanctions Russian military shipbuilder, diamond miner

White House national security adviser Jake Sullivan said there are no signs that China has given any military assistance to Russia to help with the war in Ukraine.

President Joe Biden held a video call with Chinese President Xi Jinping on Friday and Sullivan met with his counterpart in Rome on Monday over U.S. concerns that Beijing would aid Moscow.

Over a week ago, the U.S. confirmed that Russia asked China for military support and other aid since the invasion began.

"What I can tell you is we have not seen … the provision of military equipment by China to Russia," Sullivan said. "The president made clear to President Xi the implications and consequences of any such provision of equipment, and they very well understand one another."

When pressed on whether NATO allies would "put specific concrete steps in place" if China does provide assistance, Sullivan said Biden would be consulting with NATO and the EU.

“On April 1, the European Union is having a summit with China. And so this will be an opportunity, Thursday, for the United States and our European partners, to coordinate closely on what our message is. We believe we're very much on the same page with our European partners, and we will be speaking with one voice on this issue," Sullivan said.

-ABC News' Elizabeth Schulze

National security adviser Jake Sullivan said President Joe Biden and NATO allies will roll out new coordinated plans on Thursday in response to Russia's continued invasion.

Sullivan said Biden is traveling to Europe "to ensure we stay united" with our allies and to send a message that they are committed to help Ukraine "for as long as it takes."

"There will be hard days ahead in Ukraine. Hardest for the Ukrainian troops on the front lines and the civilians under Russian bombardment. This war will not end easily or rapidly," Sullivan said.

Sullivan said NATO allies will announce new sanctions, tighten existing ones, adjust troops on the Eastern Flank and outline plans to reduce Europe’s dependence on Russian energy.

Sullivan did not disclose any specific details about the sanctions but hinted that new ones will focus on a joint effort to crack down on countries helping Russia "undermine, weaken or get around the sanctions," calling it an "important part" of this next phase.

"We have applied an enormous amount of economic pressure, and in order to sustain and escalate that pressure over time, part of that is about new designations, new targets, but a big part of it is about effective enforcement and evasion, applying the lessons that we've learned from other circumstances where we have, in fact, imposed sanctions on countries," Sullivan said.

In Poland, Sullivan said Biden will "engage" with U.S. troops, hold a bilateral meeting with President Duda and meet with experts involved in the humanitarian response.

-ABC News' Justin Gomez

Ukrainian President Volodymyr Zelenskyy addressed Italy's Parliament on Tuesday, warning that "Ukraine is the gateway to Europe for Russian troops."

He called for more sanctions so Russia "is looking not for military reserves or mercenaries somewhere in Libya or Syria, but for peace."

"This is a war that Russia has been preparing for a long time. Which one person has been preparing for a long time. One! For decades," Zelenskyy said. "Their goal is Europe."

Zelenskyy compared the Russian invasion to the Nazis, saying, "The last one who did something like this in Europe were the Nazis, when they invaded other countries."

-ABC News' Christine Theodorou

For the first time since the invasion of Ukraine, Russia's combat capability has likely fallen below 90%, a senior U.S. defense official told reporters. The official said there are no tangible indications of reinforcements being brought in from elsewhere in the country.

"[This is] combat power that they assembled in Belarus and in the western part of their country prior to the invasion. It is not an assessment of all Russian military power," the official said.

The official said there are "indications" that Ukrainian resistance is trying to retake some territory seized by Russian troops, such as the town of Izyum.

"What we're starting to see are indications that they are now able and willing to take back territory that the Russians have taken," said the official. "Whether this is a part of some sort of larger operational plan, we can't say for sure."

In Mykolaiv, northeast of Odessa, the Russians have been forced to reposition themselves to the area south of the city because Ukrainian resistance was so strong north of the city, the official said.

The logistical and resupply issues continue to plague Russian troops with the official noting that Russia now has concerns about fueling its ships in the Black Sea. Frostbite has also become an issue for Russian troops who continue to be inadequately supplied.

Ukrainian forces have mounted a strong resistance inside of Mariupol against the "significant number" of Russian forces that have made their way into the city, according to the official.

“The Ukrainians are fighting very, very hard to keep Mariupol from falling,” said the official.

Russia has fired more than 1,100 missiles in Ukraine, according to the official.

-ABC News' Luis Martinez