NATO leaders are expected to call on China to refrain from supporting Russia over its invasion of Ukraine when the alliance members gather on Thursday for an extraordinary summit meeting, Secretary General Jens Stoltenberg said.

"Allies are concerned that China could provide material support for the Russian invasion," the head of the North Atlantic Treaty Organization told a press conference Wednesday, indicating members of the security bloc share Washington's worries that China is considering assisting Russia with military equipment in the conflict.

People are pictured inside a shelter as an air-raid alarm is heard amid Russian attacks in Lviv, western Ukraine, on March 22, 2022. (Kyodo) ==Kyodo

Stoltenberg pointed out that Beijing has not condemned the invasion and has also provided "political support" to Moscow by helping spread misinformation that could be damaging to Ukraine.

"I expect leaders will call on China to live up to its responsibilities as a member of the U.N. Security Council. Refrain from supporting Russia's war effort. And join the rest of the world in calling for an immediate, peaceful end to this war," he said.

With Russia's attack against Ukraine having continued for nearly a month now, leaders of NATO, the Group of Seven industrialized nations and the European Union will gather in Brussels for a series of meetings on Thursday to showcase their unity against what they view as unprovoked and unjustified aggression.

Jens Stoltenberg, secretary general of the North Atlantic Treaty Organization, speaks at a press conference at NATO headquarters in Brussels on June 7, 2018. (Kyodo) ==Kyodo

U.S. President Joe Biden will take part in all three meetings, while Japanese Prime Minister Fumio Kishida will attend the G-7 summit.

The G-7 leaders are set to agree on an initiative to coordinate the enforcement of economic sanctions imposed on Russia in the wake of its launching of the attack, White House National Security Adviser Jake Sullivan told reporters aboard Air Force One.

The move is intended to deal "effectively" with Russian efforts to evade the sanctions, Sullivan said. He also noted that the initiative is "specifically not about China" but will apply to "every significant economy" that seeks to undermine or weaken the impact of the punitive measures.

The United States, meanwhile, stepped up its condemnation of Moscow's brutality in the invasion, with Secretary of State Antony Blinken issuing a statement that Washington assesses the Russian military to have committed war crimes in Ukraine.

"Russia's forces have destroyed apartment buildings, schools, hospitals, critical infrastructure, civilian vehicles, shopping centers, and ambulances, leaving thousands of innocent civilians killed or wounded. Many of the sites Russia's forces have hit have been clearly identifiable as in-use by civilians," Blinken said.

"The deliberate targeting of civilians is a war crime," he added.

Amid no signs of the war ending, Stoltenberg highlighted the importance of ensuring it does not escalate beyond Ukraine and become a conflict between NATO and Russia.

The 30-member NATO is expected to agree during their summit to strengthen its posture in "all domains," with "major increases" planned to its forces in the eastern part of the alliance, the secretary general said.

Four new multinational battlegroups will be positioned in Bulgaria, Hungary, Romania and Slovakia, he said. Following Russia's annexation of Crimea from Ukraine in 2014, four battlegroups had already been deployed in the three Baltic states and Poland.

Russia began the military campaign against Ukraine after asserting that its security was under threat from NATO's eastward expansion and the possibility of Ukraine joining the security alliance.

Russian President Vladimir Putin sent the country's troops into Ukraine on what he called a "special military operation" meant to "demilitarize and denazify" the former Soviet republic.

Related coverage:

Zelenskyy calls for Japan sanctions on Russia to stop "tsunami" of invasion

Biden warns Russia could use chemical weapons in Ukraine

Ukraine seeks more aid in war, urges Biden to be "leader of peace"