Russia-Ukraine updates: Putin suspends key US-Russia nuclear treaty

Ukraine’s minister of defense warned his western partners Sunday that if they "procrastinate" over the supply of aircraft to Ukraine, more Ukrainians will die.

"If we will have a procrastination or reluctance with aircraft platforms, it will cost us more lives, more blood of Ukrainians," Oleksiy Reznikov told reporters in Kyiv.

Reznikov appeared to concede that the most readily available and Ukraine's preferred western aircraft, American F-16s, were no longer an option on the table with western partners.

He said Sweden’s Gripen fighter jets are still an option. Ukrainian officials have previously mentioned the Gripen as a possibility in conversations with ABC News about weapons supplies.

"I’m sure we will have (western) aircraft," Reznikov said.

Reznikov also spoke of the fierce fighting being wage in the city of Bakhmut in the Donbas region of eastern Ukraine.

Reznikov described the city as a “stronghold” which Russia has been trying to occupy for months.

Reznikov said 500 Russian soldiers a day are being injured or killed in the fight for Bukhmut and that Ukrainian casualties are significantly lower.

Any strategic decision on whether or not to withdraw, Reznikov said, would be made by Ukrainian generals and is "not a political decision."

-ABC News Tom Soufi Burridge

Israeli Prime Minister Benjamin Netanyahu said in an interview Saturday that he is considering sending to Ukraine an Iron Dome defense system.

Netanyahu told French broadcasters TF1 and LCI that he is "looking into" sending Ukraine the mobile all-weather air defense system that has helped protect his country from Palestinian rockets launched from the Gaza Strip.

"I said I’m looking into it and I’m doing just that," Netanyahu said during a visit to France.

In October, the Ukrainian government sent Israel an official request for the Iron Dome system to fend off Iranian ballistic missiles and attack drones used by Russia in Ukraine.

Netanyahu did not disclose a timeframe for when the defense system might be sent to Ukraine, saying, he is reviewing the request from Ukraine and the overall policy for supplying the system.

At least five people were injured Sunday when Russian missiles hit a residential building and a university in central Kharkiv, Ukraine's second largest city, Ukrainian officials said.

Kharkiv Regional Gov. Oleh Syniehubov said four people were hurt when a Russian missile landed near an apartment building in central Kharkiv, according to The Associated Press.

Syniehubov said one other person was injured in a missile strike on a building at the National Academy for Urban Economy, a university near Kharkiv's central square.

The missile strikes prompted the evacuation of local residents, Syniehubov said.

"In short, there was a strong blast, and it was just one short moment and everything happened," one of the evacuees, Lyudmyula Krylova, told Reuters.

Krylova said she was in the residential building near where the missile landed.

"We were saved by the furniture that fell on us, and because of this we are now alive," said Krylova, adding that a friend was injured in the attack and taken to a hospital.

Meanwhile, fighting intensified Sunday in the eastern Ukrainian city of Bakhmut, Yevgeny Prigozhin, leader of the private Russian military company, the Wagner Group, said in a statement posted on Telegram.

Prigozhin denied reports that Ukrainian forces were retreating from the area. He said the Ukrainian troops were fighting for “every street, every house, every stairwell.”

An American volunteer medic was killed in Ukraine on Thursday while helping civilians evacuate, according to his family and Global Outreach Doctors, the humanitarian organization he was volunteering with.

Pete Reed, 33, died after his evacuation vehicle was hit with a reported missile in Bakhmut in eastern Ukraine, according to Global Outreach Doctors.

"Pete was a beacon of humanitarian work -- an incredible visionary, leader, compassionate care provider, and an inspiration to us all," Global Outreach Doctors founder and president Andrew Lustig said in a statement on social media Friday. "He selflessly dedicated his life in service to others, especially those affected by disaster and war. Pete accomplished more in his 33 years than most of us in our entire lives. He leaves behind an incredible legacy."

His family said that Reed was responding to wounded civilians when his ambulance was shelled.

"He died doing what he was great at, what gave him life, and what he loved, and apparently by saving a team member with his own body," his family said in a statement shared to social media on Friday. "As you can imagine we are all in shock and have much to do to get him home so we ask for privacy presently."

Reed was a former U.S. Marine who joined Global Outreach Doctors in January to serve as its Ukraine country director, Lustig said.

The State Department did not name Reed directly, in accordance with its standard privacy practices, though a spokesperson confirmed the death of a U.S. citizen in Ukraine and said that officials from the department "are in touch with the family and providing all possible consular assistance."