Canada announced a new program on Thursday that will "cut through red tape" to expedite arrivals for Ukrainians seeking temporary or permanent residency, said Sean Fraser, Canada's minister of immigration, refugees and citizenship.

"There is no limit on how many can apply," Fraser said.

"All those who arrive in Canada as part of these measures will be eligible for open work permits and will quickly be able to work if they so choose," Fraser noted.

He went on, "Our commitment to Ukrainians goes beyond the historic ties between Canada and Ukraine and beyond the cultural connections between our people. It's a commitment to humanity."

-ABC News' Christine Theodorou

The U.S. Treasury and State Departments are expected to announce new sanctions against Russian oligarchs on Thursday, according to a White House official.

The sanctions will expand upon recently announced EU sanctions, block specific oligarchs’ travel to the U.S. and target the oligarchs’ relatives, according to the official.

-ABC's Ben Gittleson

One week into the conflict, half a million children have already fled Ukraine to neighboring countries with the number continuing to grow, the United Nations International Children's Emergency Fund said on Thursday.

"Millions of children could be caught up in the violence as the fighting intensifies in and around the country’s major urban centers," UNICEF said in a statement.

Since Feb. 24, 17 children have been killed and 30 others have been injured, according to reports the UN has been able to verify. UNICEF said the true number of casualties is "likely far higher."

“The use of explosive weapons in cities could quickly turn this crisis into a catastrophe for Ukraine’s children,” said Afshan Khan, UNICEF’s Regional Director for Europe and Central Asia.

“There are no armed operations of this scale that do not result in children being harmed. The consequences will be tragic,” Khan said.

The conflict has sparked massive population displacement that could soon constitute one of Europe’s largest refugee crises since World War II, UNICEF warned.

UNICEF said hundreds of homes have been damaged or destroyed and there are reports of schools, orphanages and health centers sustaining heavy damage.

"Humanitarian needs across the country are multiplying by the hour," UNICEF said.

The country is running low on critical medical supplies and has had to halt urgent efforts to curb a polio outbreak, UNICEF said.

- ABC News' Christine Theodorou

When asked by reporters how long Ukraine can hold out against the Russian advance, Ukraine President Volodymr Zelenskyy said "I don't know."

In a press conference on Thursday reporters asked the president if he would ever leave Kyiv, Zelenskyy said "no!"

Zelenskyy said he's ready to meet and talk directly with Russia President Vladimir Putin and stressed once again the need for a 'no-fly' zone immediately over the entire country, saying it would act as a deterrent.

He paid tribute to the valor of Ukrainian forces and appealed to Russian mothers not to send their sons to die on foreign soil.

Zelenskyy also thanked President Joe Biden for the continuing support, but criticized the West for being late to introduce sanctions that he believes could’ve prevented the Russian invasion in the first place.

-ABC News' Ian Pannell

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