BEIJING (AP) — China on Wednesday sharply criticized a visit to Taiwan by a senior Pentagon official and reaffirmed it has sanctioned Lockheed Martin and a unit of Raytheon for supplying military equipment to the self-governing island democracy.

The comments from the Cabinet’s Taiwan Affairs Office underscore the dramatic deterioration in relations between Beijing and Washington over Taiwan, technology, spying allegations, and, increasingly, Russia’s invasion of Ukraine.

Asked about the reported visit by Michael Chase, deputy assistant secretary of defense for China, office spokesperson Zhu Fenglian said China “resolutely opposes any official interaction and military collaboration” between the U.S. and Taiwan.

Efforts by Taiwan’s ruling Democratic Progressive Party to cement the island’s independence with foreign assistance are “doomed to failure,” Zhu told reporters.

China considers Taiwan part of its territory to be brought under its control by force if necessary, and has been stepping up its military and diplomatic harassment. The sides split amid civil war in 1949, and China’s authoritarian Communist Party has never held sway over the island.

A Pentagon spokesperson did not comment directly on Chase’s visit, repeating that “our commitment to Taiwan is rock-solid and contributes to the maintenance of peace and stability across the Taiwan Strait and within the region.” Taiwan’s Ministry of Foreign Affairs has said it had no information about any such visit.

Chinese Foreign Ministry spokesperson Wang Wenbin said a “new round of tensions” in the Taiwan Strait was a result of the Taiwanese authorities’ attempts to “seek independence with U.S. support, as well as the U.S. intention to contain China with Taiwan.”

“We urge the U.S. to … stop any form of official U.S.-Taiwan contacts, stop meddling in the Taiwan issue and stop creating new factors of tension in the Taiwan Strait,” Wang said at a daily briefing.

Tensions between the U.S. and China again ratcheted up last month after Washington accused Beijing of sending a spy balloon that was shot down over the American East Coast. Secretary of State Antony Blinken canceled a trip to Beijing in the wake of the incident and said over the weekend that the United States was concerned China would provide weapons to Russia for its war in Ukraine.

China, which has declared a “no limits” friendship with Russia, has pointedly refused to criticize Moscow’s actions, blaming the U.S. and NATO for provoking the Kremlin, and has blasted the punishing sanctions imposed on Russia. Russia, in turn, has strongly backed China over Taiwan.

On a visit to Moscow Tuesday, the Communist Party’s top diplomat Wang Yi said relations between Moscow and Beijing are “solid as a rock” and will “stand the test of the volatile international situation.”

Russia and China have an “excellent opportunity to continue close strategic cooperation and contacts to protect our shared strategic interests,” Wang said.

Wang Wenbin, the Foreign Ministry spokesperson, said he had no information about a possible visit by Chinese President Xi Jinping to Moscow this spring.

A delegation of U.S. lawmakers visiting Taiwan met on Tuesday with President Tsai Ing-wen, who said she looked for increased cooperation on issues from security to climate change.

On Monday, the delegation met with the head of the legislature as part of their five-day visit. They include Reps. Ro Khanna of California, Tony Gonzales of Texas, Jake Auchincloss of Massachusetts and Jonathan Jackson of Illinois.

The congressional team held talks with Taiwan Semiconductor Manufacturing Company’s founder Morris Chang, considered the father of the island’s world-leading microchip industry that is now investing heavily in U.S. production.

Khanna and Auchincloss are both members of the new House select committee focused on competition with China.

Amid the flurry of exchanges, Taiwan’s Foreign Minister Joseph Wu and head of the National Security Council Wellington Koo were in Washington on Tuesday for what are believed to be security meetings.

They were filmed by Taiwan’s private TVBS television station entering the offices of the body the U.S. uses to oversee relations with Taiwan in lieu of formal diplomatic ties. Washington cut formal relations in 1979 in order to establish ties with Beijing, but remains the island’s chief political and military ally.

China has increasingly lashed back at the increase in exchanges with Taiwan by officials and elected representatives from the U.S. and other democratic nations. China’s campaign of diplomatic isolation has left Taiwan with just 14 formal allies, although it retains robust unofficial relations with dozens of other countries.

Last Thursday, China imposed trade and investment sanctions against Lockheed Martin Corp. and Raytheon Technologies Corp.’s Raytheon Missiles and Defense, barring them from importing goods into China or making new investments in the country.

The Ministry of Commerce declared they had been added to the “unreliable entity” list of companies whose activities are restricted because they might endanger national sovereignty, security or development interests. It wasn’t clear what impact the penalties would have.

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