WASHINGTON >> President Joe Biden on Thursday announced that the U.S. will send Ukraine another $800 million in security assistance to help it stave off Russia’s renewed offensive in the country’s eastern Donbas region.The tranche of defense aid, which follows a similar $800 million package last week, will include more heavy artillery and offensive weaponry that Ukrainian President Volodymyr Zelenskyy has requested as the war shifts into a ground conflict that could go on for months.

The package brings the total amount of U.S. defense assistance for Ukraine since the war began to $3.4 billion, a sign of the Biden administration’s desire to see the small eastern European democracy survive Russia’s unprovoked assault.

“We’re not sitting on the funding that Congress has provided for Ukraine. We’re sending it directly to the frontlines of freedom,” Biden said in a speech from the White House during which he announced the U.S. would provide Ukraine with an additional $500 million in humanitarian aid.

Meanwhile, Russia claimed victory over the battered southern Ukrainian port of Mariupol on Thursday, with President Vladimir Putin saying he had ordered his forces not to attack the city’s last holdouts sheltering in a vast steelworks but to blockade the compound so tightly that “not even a fly comes through.”

Ukraine’s government rejected the Russian assertion of a complete takeover of the once-thriving coastal city, which has been nearly wiped out in the course of nonstop attack. But Putin’s announcement that troops would not storm the sprawling Azovstal steel plant — where Ukrainian forces and civilians are holed up — was at once a sign of Russian confidence in its grip on Mariupol and of the fierce resistance of local defenders who have refused the enemy’s demands to surrender.

Zelenskyy told a French television station Thursday that “local residents, children, the elderly and the military are blocked in the city of Mariupol.”

“It is not more like a war, but a terrorist operation by Russia against Mariupol and the people of this city,” he said.

Speaking Thursday at the White House, Biden said it was “questionable” whether Putin controlled the city.

“There is no evidence yet that Mariupol has completely fallen,” said Biden, who predicted that the Russian offensive was “going to be limited in terms of geography but not limited in terms of brutality.”

Ukrainian officials said Thursday that there would be additional attempts to evacuate civilians from the region. They also said they wanted to negotiate the status of the city.

Speaking on the messaging app Telegram, Deputy Prime Minister Iryna Vereshchuk said that “we demand from the Russians an urgent humanitarian corridor from the Mariupol plant Azovstal. There are now about 1,000 civilians and 500 wounded soldiers. They all need to be removed from Azovstal today.”

The latest U.S. military assistance, Biden said, includes dozens of howitzers and 144,000 rounds of ammunition for the long-range ground weapons, as well as more drones.

Biden, however, said he has “exhausted” his drawdown authority to approve more aid for Ukraine and planned to ask Congress next week to expand his ability to continue to send assistance. He also announced that the U.S. was banning any Russian ships from American ports.

He said that Putin appears to be betting that the West will lose its focus and resolve as the war drags on and vowed that “we’re going to prove him wrong.”

He continued: “We will not lessen our resolve. We’re going to continue to stand with the brave and proud people of Ukraine. We will never fail in our determination.”

After responding initially to Putin’s invasion primarily with economic sanctions, which the U.S. and its NATO allies have continued to ratchet up, Biden and other NATO leaders have shown a growing willingness to arm Ukraine as it has become clear the war could be a prolonged one.

“This is our responsibility, it seems to me,” he said.

Ukraine’s resilience in battle has come as something of a surprise, as has Zelenskyy’s remarkable effectiveness in using Western media to rally global support for his country’s cause. Zelenskyy’s efforts have prompted the leaders of the world’s largest democracies to back up their rhetoric with action.