US President Joe Biden on Friday publicly apologised for the first time for months-long delays in US military aid to Ukraine that helped Russia gain an edge on the battlefield, while Ukrainian President Volodymyr Zelensky appealed for bipartisan American support “as it was during World War II.”

Speaking in Paris a day after attending the 80th anniversary of D-Day in Normandy, Mr. Biden apologized to the Ukrainian people for the weeks they spent not knowing if further aid would come while conservative Republicans in Congress held up a $61 billion military aid package for Ukraine for six months.

Still, the Democratic president insisted the American people stand with Ukraine for the long haul. “We’re still with it. Totally. Totally,” he said.

Mr. Zelenskyy stressed the need for all Americans to support his country’s defense against Russian aggression, and he thanked lawmakers for ultimately approving the weapons package that has helped Ukraine fend off Russian advances in recent weeks.

“It is very important that in this unity, the United States, all the American people stand with Ukraine, as it was during the Second World War,” Mr. Zelensky said. “How the United States helped save human lives, save Europe. And we count on your continued support in standing with us, shoulder to shoulder.”

The United States is by far the biggest provider of wartime aid to Kiev, and Ukraine is trying to fend off Russia’s rapid advance into the country’s eastern regions. The effort is focused on the Ukrainian border regions of Kharkiv and Donetsk, but Ukrainian officials say it could spread as Russia’s large military seeks to show its advantage.

The offensive aims to exploit shortages of ammunition and troops along Kiev’s nearly 1,000-kilometre (620-mile) front line.

The weapons shortage comes after US military aid was stalled in Congress for six months before Mr Biden signed a $61 billion package into law in April.

The slow pace of promised Western weapons deliveries has long frustrated Mr. Zelensky, as has Mr. Biden’s hesitancy to supply more hardware for fear of provoking Russian President Vladimir Putin. That has strained their relationship.

The United States will send nearly $225 million in military aid to Ukraine, US officials said Thursday. The latest package includes ammunition for the High Mobility Artillery Rocket System, or HIMARS, as well as a range of mortar systems and artillery rounds, officials said.

Softening their stance amid Russia’s recent offensive and the worsening situation of Ukraine’s military, some NATO allies including the United States said last week they would allow Ukraine to use weapons supplied to Kiev to carry out limited strikes inside Russia.

The move prompted a sharp reaction from the Kremlin, which warned that Europe’s biggest conflict since World War II could spiral out of control.

Mr. Biden and Mr. Zelensky attended D-Day anniversary events in Normandy, northern France, on Thursday, along with European leaders who have backed Kiev’s efforts in the war. Mr. Biden vowed that “we will not back down from Ukraine,” drawing a direct line from the fight to free Europe from Nazi domination to today’s war against Russian aggression.

Ukraine portrays its fight against Kremlin forces as a clash between Western democratic freedoms and Russian tyranny. Russia says it is defending itself against the dangerous eastward expansion of the NATO military alliance.

In a 20-minute speech on Friday to the National Assembly, the lower house of the French parliament, Mr. Zelensky drew comparisons between the sacrifices made during World War II and his country’s current battle.

“This battle is a crossroads,” Mr. Zelensky said. “A moment where we can now rewrite history the way we need it. Or we can become victims of a history that suits our enemy.”

Mr Zelensky, who was speaking in Ukrainian, was repeatedly interrupted by applause and cheers from lawmakers as he said in French: “Dear France, I thank you for standing with us while protecting lives.”

Meanwhile, French President Emmanuel Macron announced late Thursday that France would provide its Mirage fighter jets to Ukraine.

Macron has been a vocal supporter of Ukraine. He said in February that the possibility of deploying Western troops in Ukraine could not be ruled out.

Mr. Zelensky began a day of meetings in Paris with an official reception at the gold-domed Invalides monument that houses Napoleon’s tomb.

During the day, Mr Zelensky was due to visit the Nexter weapons manufacturer in Versailles, which makes the Caesar self-propelled howitzer, one of the weapons provided by France to Kiev’s army.

He was also scheduled to meet Macron at the Elysee Palace.

Mr Zelenskyy’s foreign trips are aimed at publicising Ukraine’s plight, obtaining more military aid to fight Russian aggression, and securing long-term Western support through bilateral alliances.

France and Ukraine signed a 10-year bilateral security agreement in February. Mr. Zelensky has since signed similar bilateral agreements with several European countries.