US President Joe Biden has apologised to his counterpart Volodymyr Zelensky for delays in military aid to Ukraine and has pledged $225m (£191m) in support.
The pair met for talks in Paris, a day after they both attended the 80th anniversary commemorations of the D-Day landings in Normandy, France.
The US Department of Defense said the new aid package would include ammunition and anti-aircraft missiles.
Russia launched a full-scale invasion of Ukraine in February 2022.
Mr Biden said previous delays in aid had been caused by some Republicans in Congress, but reiterated US support for Ukraine.
“The United States will stand with you,” Mr Biden told Mr Zelensky. “You haven’t bowed down. You haven’t yielded at all. You continue to fight in a way that is just remarkable, just remarkable.”
In response, Mr Zelensky stressed the importance of his country’s relationship with the US, saying it was crucial in the fight against Russia: “We count on your continuing support in staying with us shoulder to shoulder.”
After meeting Mr Zelensky, Mr Biden made a passionate speech at Pointe Du Hoc, a site in Normandy where US army rangers scaled a cliff to storm a Nazi stronghold on D-Day.
The US president spoke about the sacrifice of those who lost their lives on 6 June 1944, saying: “Does anyone doubt that they would want America to stand up against Putin’s aggression here in Europe today?”
“They’re asking us to do our job: to protect freedom in our time, to defend democracy, to stand up to aggression abroad and at home,” he added.
Earlier in the day, Mr Zelensky addressed the French parliament, saying the current conflict with Russia meant Europe was “unfortunately no longer a continent of peace”.
He also expressed hope that a summit hosted in Switzerland later this month could help bring an end to the war.
The Ukrainian president is due to meet with French President Emmanuel Macron during his visit.
Speaking on French TV on Thursday evening, Mr Macron said Paris would send Mirage 2000 fighter jets to Ukraine and train Ukrainian pilots. He said training could begin this summer.
“You need normally between five, six months. So by the end of the year there will be pilots. The pilots will be trained in France,” he said.
Mr Macron also said Western allies would consider a request to send military instructors to train Ukrainian forces on the ground.
Kremlin spokesman Dmitry Peskov said the French president’s comments showed that he was willing to take a “direct” role in the Ukraine conflict.
Friday’s developments come a day after Russian President Vladimir Putin warned that Moscow could arm countries with a view to attacking Western targets.
Mr Putin made the statement while criticising the West’s delivery of long-range weapons to Ukraine. He did not specify which countries Moscow could supply with weapons.
Several countries including the US have given Ukraine the green light to strike targets inside Russia.
Mr Biden has given Ukraine permission to use American-supplied weapons to strike targets in Russia, but only near the Kharkiv region. The White House has said Ukraine cannot use long-range ATACMS missiles on Russian soil.