Russian forces have attacked Ukrainian communications infrastructure to "reduce Ukrainian citizens' access to reliable news and information," the U.K. Ministry of Defence said on Monday.

"Russia reportedly struck a TV tower in Kharkiv yesterday, suspending broadcasting output," the Ministry’s update said.

Russian forces on March 1 struck a TV tower in Kyiv, the capital.

Russia declared a cease-fire starting Monday morning, opening humanitarian corridors for the evacuation of civilians from Kyiv, Mariupol, Kharkiv and Sumy, the Russian interagency humanitarian response staff in Ukraine said.

"Taking into account the disastrous humanitarian situation and its severe deterioration in the cities of Kyiv, Kharkiv, Sumy, and Mariupol, and also at French President Emmanuel Macron's personal request to Russian President Vladimir Putin, the Russian Armed Forces are declaring a ceasefire and opening humanitarian corridors for reasons of humanity starting 10:00 a.m. on March 7, 2022," the staff said.

Ukrainian officials in Mariupol said Russia broke planned cease-fires on Saturday and Sunday. Russia's announcement on Monday of humanitarian corridors was "unacceptable," a Ukrainian official said, saying all of Russia's planned routes led to Russia.

The Ukrainian armed forces have received approximately 3,000 applications from the U.S. to join the fight against invading Russian troops, a Ukrainian Embassy official confirmed to ABC News.

Voice of America was first to report the news this weekend.

-ABC News’ Conor Finnegan

In a new letter to House Democrats, Speaker Nancy Pelosi reiterated plans to approve new aid for Ukraine in a government funding measure this week.

She also said new legislation to ban the import of Russian oil and energy products would repeal normal trade relations with Russia and Belarus and deny Russia access to the World Trade Organization.

The measure would also give the administration more power to raise tariffs on Russian imports.

Pelosi said Congress and the Biden administration “remain laser-focused on bringing down the higher energy costs for American families and our partners,” noting that 60 million barrels of oil have been released from strategic reserves and allies have said they will reduce their dependence on Russian energy.

“With the West’s carefully coordinated effort to sequence sanctions on Russia and mitigate for the costs of these efforts, we are standing up for our values abroad while protecting our families at home,” Pelosi wrote in the letter.

It’s not clear when the House will take up this measure, but Congress needs to approve government funding -- which will include the Ukraine aid -- by Friday.

-ABC News’ Ben Siegel

The Russian forces charging toward Kyiv haven't made progress in the last day as they face Ukrainian resistance and low food and gas supply, a senior U.S. defense official told reporters Tuesday.

However, it could be a deliberate pause, the official said. "Part of the stall could be ... as a result of their own self-determined sort of pause in operations -- that they are possibly regrouping, rethinking, reevaluating," the official said.

The U.S. believes Russian forces "have committed now more than 80% of what was their pre-staged combat power," the official added.

The official said some Russian soldiers weren't told they were going into combat. The official said "not all of them were apparently fully trained and prepared."

The strong Ukrainian resistance has also hurt morale, according to the official.

Russia has now launched more than 400 missiles on Ukraine, the official said. The U.S. believes Russia has launchers that could be used for thermobaric weapons, but cannot confirm their use, the official said.

Russian forces are making the most progress in the south. Russians are attacking Kherson in south Ukraine, which "appears very much to be contested city at this point," the official said.

Russians are also approaching Mariupol in southeastern Ukraine, and while they haven't yet entered the city, "they are close enough now that they could attack Mariupol with long range fires," the official said.

Two towns on the path to Mariupol are believed to be occupied by the Russians, according to the official.

The U.S. believes the Russians hope to move north out of Mariupol up to the heavily-contested city of Kharkiv. The official said they believe Russian forces are trying to encircle Kharkiv.

The U.S. official noted that they've seen "certain risk-averse behavior by the Russian military" over the last week.

"Take the amphibious assault, for instance. They put those troops ashore a good 70 kilometers away from Mariupol because they knew Mariupol was going to be defended and they could put them ashore in an uncontested environment. And they still haven't reached Mariupol," the official said.

"They are not necessarily willing to take high risks with their own aircraft and their own pilots," the official said.

"And of course we're seeing that on the ground -- the fairly slow and steady progress that they have made, and you guys are seeing it for yourselves on the ground where ... units are surrendering, sometimes without a fight."

-ABC News' Matt Seyler