U.S. National Security Adviser Jake Sullivan will meet with China's top diplomat Yang Jiechi in Rome on Monday to discuss Russia's war against Ukraine and its impact on regional and global security, a source familiar with the plans said.

The meeting had been in planning for some time as part of a broader effort by Washington and Beijing to maintain open channels of communication and manage competition, but the war in Ukraine would be "a significant topic," the source said.

"This meeting is taking place in the context of Russia's unjustified and brutal war against Ukraine, and as China has aligned itself with Russia to advance their own vision of the world order, and so I expect ... the two of them will discuss the impact of Russia's war against Ukraine on regional and global security," the source said.

No specific outcomes were expected from the meeting, the source added, speaking on condition of anonymity.

"It is important for (People's Republic of China) officials to hear directly from the national security adviser his assessment of how we see the situation," the source said.

The United States on Saturday said it would rush up to $200 million worth of additional weapons to Ukrainian forces as they try to defend against Russian shelling in the largest war in Europe since World War Two.

The Russian assault, which Moscow calls a "special military operation," has trapped thousands of civilians in besieged cities and sent 2.5 million Ukrainians fleeing to neighboring countries.

The United States and its allies have imposed sweeping, unprecedented sanctions against Russia and banned its energy imports, while providing billions of dollars of military and humanitarian assistance to Ukraine.

Individually and together they have appealed to China, Gulf nations and others that have failed to condemn the Russian invasion to join in isolating Russia from the global economy.

Beijing, a key trading partner of Russia, has refused to call Russia's actions an invasion, although Chinese President Xi Jinping last week did call for "maximum restraint" in Ukraine after a virtual meeting with German Chancellor Olaf Scholz and French President Emmanuel Macron.

Xi also expressed concern about the impact of sanctions on global finance, energy supplies, transportation and supply chains, amid growing signs that Western sanctions are limiting China's ability to buy Russian oil.

The International Monetary Fund last week warned that the crisis could also see China miss its 5.5% growth target this year, and its chief said she had spoken with China's top central banker and expected mounting pressure on Russia to end the war.

While in Rome, Sullivan will also meet with Luigi Mattiolo, diplomatic adviser to Italian Prime Minister Mario Draghi to continue coordinating the strong global response to Russian President Vladimir Putin's "war of choice," the source said.

The United States and the Group of Seven advanced economies on Friday ratcheted up pressure on Russia by calling for revoking its "most favored nation" trade status, which would allow them to jack up tariffs on Russian goods.

Trade made up about 46% of Russia's economy in 2020, much of that with China, its biggest export destination.