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

Russian President Vladimir Putin signed a decree Tuesday that not only rejects a price cap on the country's oil but bans sending crude and other petroleum products to any country that has endorsed the price cap.

The Group of Seven countries, including the United States, agreed on Dec. 3 to impose a $60 per barrel price cap on Russian oil in response to the Kremlin's invasion of Ukraine. Australia and the European Union also agreed to impose the price cap.

The decree Putin signed goes into effect on Feb. 1 and is valid until July 1, 2023.

The decree bans the supply of oil and oil products from Russia to those countries that place a price ceiling on contracts. The decree also forbids the supply of oil to other foreign buyers whose contracts use a price cap mechanism.

The decree includes a clause allowing Putin to overrule the ban in special cases to be determined by the Russian leader.

The price cap on Russian oil implemented by G-7 nations disallows the world's second-largest oil exporter from selling crude at a price above $60 per barrel.

Since the outset of its war with Ukraine, Russia has sold its oil at discounted prices. As of Tuesday, Russian Urals crude was trading at $57 per barrel -- an amount slightly less than the cap. But the price cap aims to ensure that Russian oil sales remain well below global oil prices, which stand at about $80 per barrel.

-ABC News' William Gretsky

Ukraine's foreign minister said in an interview with The Associated Press that he would like to have a peace summit in February, the one-year anniversary of the war, and would like it to be held at the U.N.

"The United Nations could be the best venue for holding this summit, because this is not about making a favor to a certain country," Dmytro Kuleba told the AP. "This is really about bringing everyone onboard and there is no better place than the United Nations to do that."

He continued, "Every war ends in a diplomatic way. Every war ends as a result of the actions taken at the battlefield and at the negotiating table. But the balance of what will be won on the battlefield and what will be won at the table, it remains to be seen."

Russia has so far rejected serious peace talks with Ukraine.

Meanwhile, Ukraine is calling for Russia to be expelled from the U.N. Security Council.

Ukrainian politician Iouri Loutsenko, the country's former prosecutor general, is leading the legal push to remove Russia as a permanent member of the U.N. Security Council: "It's about world peace. It's about world security, and it's about the rule of law in the world."

Loutsenko and his team argue that Russia's membership is illegitimate because the seat was initially granted to the Soviet Union in 1991, not the Russian Federation.

"In very simple terms, we have every legal argument to prove that Russia has never become a legitimate member of the U.N.," he told ABC News.

-ABC News' Britt Clennett

A Ukrainian drone attack on the Engels Air Force Base in southern Russia killed three, Russia’s Ministry of Defense said.

A spokesman for Ukrainian Air Force confirmed the attack, saying, “If the Russians thought the war would not touch them they were wrong.”

Russian air defence reportedly shot down a Ukrainian drone flying at low altitude, but falling debris caused the casualties in the overnight attack.

The Engels base lies just over 300 miles northeast of Ukraine's border with Russia. The facility has been repeatedly used by Russia to carry out missile strikes on targets in Ukraine.

Ukrainian forces had attacked another Russian air base on Dec. 5, killing three and damaging two strategic bombers.

-ABC News’ Britt Clennett

The Pentagon is weighing whether to carry out Patriot missile training for Ukrainian troops inside the United States, according to two U.S. officials.

If so, it would mark the first time Ukrainian forces trained inside the U.S. since the start of Russia's invasion.

The officials say the Army base at Fort Sill, Oklahoma, is being considered as the site for stateside training.

Last week, a senior defense official told reporters that several options were being considered for training that could last several months. However, no decision has been made and it is still possible that the training may take place in Germany, as previously reported.

Weapons systems training for Ukrainian troops has taken place only in Ukraine.

- ABC News' Luis Martinez