The U.S. State Department on Saturday updated its travel advisory for Russia amid the war in Ukraine and Russia's tightening crackdown on dissent, reporting and travel and the worsening economic situation, including declined credit cards and cash shortages.

"U.S. citizens should depart immediately," the advisory warns, adding, "If you wish to depart Russia, you should make arrangements on your own as soon as possible."

The State Department warned Americans, "If you plan to stay in Russia, understand the U.S. Embassy has severe limitations on its ability to assist U.S. citizens, and conditions, including transportation options, may change suddenly."

The State Department further warned U.S. citizens may be harassed by "Russian government security officials" or face "arbitrary enforcement of local law," something they've warned about for years.

The U.S. embassy has issued detailed instructions on how to flee the country, including over land borders by car and bus as well as limited flights.

-ABC News' Conor Finnegan

Russia’s Defense Ministry on Saturday announced it will now begin offensive actions again in Ukraine, having never observed the cease-fire it announced earlier in the morning.

A Defense Ministry spokesman, in a briefing, accused Ukraine’s government of failing to restrain “nationalists” or observe the cease-fire saying, “at 18:00 Moscow-time offensive actions are renewed.”

In reality, Russia has continued to shell Mariupol and Volnovakha in Ukraine’s east throughout the day, despite having declared a temporary cease-fire and humanitarian corridor to allow civilians to leave.

Ukrainian officials have accused Russia of using the cease-fire period to move forces closer to Ukrainian positions.

The International Committee of the Red Cross has said evacuations could not take place today because of shelling. The ICRC branch in Donetsk told ABC News earlier, that its team in Mariupol was forced to take shelter because of shelling.

-ABC News' Patrick Reevell

Ukrainian President Volodymr Zelenskyy spoke to over 300 senators, members of Congress and top Hill staff on Saturday, pleading for more lethal and military aid.

Zelenskyy, on an hourlong Zoom call, asked U.S. lawmakers for weapons including drones, planes and stingers; the implementation of a "no-fly" zone over Ukraine; a full ban on the import of Russian oil to the U.S.; and a suspension of the use of Visa and MasterCard in Russia.

In a statement made after the call, Senate Majority Leader Chuck Schumer said, “President Zelenskyy made a desperate plea for Eastern European countries to provide Russian-made planes to Ukraine. These planes are very much needed. And I will do all I can to help the administration to facilitate their transfer.”

According to a source who attended the meeting, Schumer started the call by addressing Zelenskyy, saying, “Mr. President, we are inspired by you and the strength and courage of the Ukrainian people. The people of New York and its large Ukrainian community stand with you."

“Senator McConnell and I, along with the other members on this zoom, are working very hard in a bipartisan fashion to get all the assistance the administration has requested for the Ukrainian people. Together we will get that assistance of over $10 billion in economic, humanitarian and security assistance to the Ukrainian people quickly," Schumer said.

One senator on the call told ABC News' Rachel Scott that at one point, dozens of attendees unmuted and said "Thank you, Mr President," "We support you," "Slava Ukraini" and "We will help you."

The senator told Scott that Zelenskyy "was clearly moved by the cascade of voices lifted in support."

Senators Rob Portman and Jeanne Shaheen, who recently traveled to Ukraine, are expected to send a letter asking the Department of Defense to send F16 planes to Eastern European countries who donate MiG aircrafts to Ukraine. Poland has said it is willing to do this.

Another senator told ABC News that there are serious concerns about Zelenskyy's safety, saying, "If he’s dead it makes it that much easier for Russians to seize control. If there isn’t a legitimate government we recognize it’s harder to help."

According to a source, Zelensky said he and his family have been targeted.

The U.S. Department of the Treasury said Friday that sanctions don't start until June and omit Russian oil and gas. Senators are going to call for immediate tightening.

-ABC News' Trish Turner, Rachel Scott, Mariam Khan and Ben Siegel

The U.S. on Saturday confirmed that it approved a flight chartered by the Russian government to pick up the Russian United Nations Mission personnel who were ordered expelled earlier this week for reportedly spying, State Department spokesperson confirmed to ABC News.

"This special exception was done in accordance with federal regulations to ensure Russian mission personnel and their families departed by the date we had instructed," the spokesperson said.

-ABC News' Conor Finnegan

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