Russia-Ukraine updates: Putin suspends key US-Russia nuclear treaty in speech denouncing West

NATO leaders warned Russia that it would meet attacks on allies' critical infrastructure with a "united and determined response."

In a news conference Tuesday, NATO Secretary-General Jens Stoltenberg said that while the defense alliance had not seen any changes in Russia's nuclear posture, it was vigilant and would proceed with a nuclear preparedness exercise of its own next week.

"Now is the right time to be firm and to be clear that NATO is there to protect and defend all allies. ... It would send a very wrong signal if we suddenly now canceled a routine, long-time-planned exercise because of the war in Ukraine," Stoltenberg said.

In next week's annual "Steadfast Noon" drill, NATO air forces will practice the use of U.S. nuclear bombs based in Europe with training flights, without live weapons.

Stoltenberg also pledged to boost the protection of critical infrastructure in response to the attack on the Nordstream gas pipelines, saying NATO had already doubled its presence in the Baltic and the North seas to over 30 ships supported by aircraft and undersea activities.

"We will further increase protection of critical infrastructure in light of the sabotage of the Nordstream pipelines," he said.

-ABC News' Will Gretsky

Russian forces have kidnapped Valery Martynyuk, the deputy head of the Russian-occupied Zaporizhzhia nuclear power plant in Ukraine, and are detaining him in an unknown location, Ukraine's state nuclear energy company Energoatom said Tuesday.

Russian forces are allegedly trying to get information about the personal affairs of Zaporizhzhia employees in order to force Ukrainian personnel to work at Russia's state nuclear agency Rosatom as soon as possible, Energoatom alleged in a statement to ABC News.

This incident follows the detention of Zaporizhzhia's then-chief Ihor Murashov on Oct. 1. The International Atomic Energy Agency announced his release on Oct. 3. Murashov later announced he would not return to the plant as its head.

-ABC News' Will Gretsky

Group of 7 leaders met virtually on Tuesday with Ukrainian President Volodymyr Zelenskyy, after Russia launched airstrikes on civilians and civilian areas in response to an attack on the bridge linking annexed Crimea to Russia.

"We condemn these attacks in the strongest possible terms and recall that indiscriminate attacks on innocent civilian populations constitute a war crime. We will hold President Putin and those responsible to account," G-7 leaders said in a joint statement.

The G-7 leaders also accused Russia of "blatantly" violating the U.N. Charter. The leaders also vowed to continue financial, humanitarian, military, diplomatic and legal support to Ukraine.

G-7 leaders also said they would help insure the recovery and reconstruction of Ukraine "including exploring avenues to do so with funds from Russia," according to the statement.

The leaders also condemned the deliberate attacks on Nordstream pipelines in the Baltic Sea and vowed to "act in solidarity and close coordination" to address the impact of Russia's invasion of Ukraine on the global economy.

Ahead of the Group of 20 summit in Bali, Indonesia, next month, Russia indicated it may be open to a meeting between President Joe Biden and President Vladimir Putin, Russian Foreign Minister Sergey Lavrov said in an interview with news agency Interfax.

"We have repeatedly said that we never refuse meetings," Lavrov said, according to Interfax. "If a proposal is made, it will be considered by us."

The White House National Security Council pointed to a comment made by Biden on Thursday outside the White House.

When asked by a reporter if he would meet with Putin, Biden responded, "That remains to be seen."

-ABC News' Anastasia Bagaeva and Ben Gittleson