March 1 (UPI) -- A delegation of former United States defense officials arrived in Taiwan on Tuesday afternoon in an unofficial visit seen as a show of support for the democratic, self-governing island amid the growing threat from China.
A five-person team, led by former Chairman of the Joint Chiefs of Staff Mike Mullen, will meet with Taiwanese President Tsai Ing-wen and other senior officials during a two-day visit, Taiwan's presidential office said in a statement.
"We would like to express our sincere thanks to President Biden and the U.S. government for their firm support for Taiwan," presidential spokesman Chang Tun-han said. "Especially at a time when the situation in Ukraine is severe, [the visit] shows that Taiwan-U.S. relations are rock-solid."
Russia's invasion of Ukraine has brought a renewed focus on the danger to Taiwan posed by China, which has vowed to retake the island it views as a breakaway province.
China said Tuesday that the visit by the delegation was "futile" and warned the United States to tread carefully in its involvement with Taiwan.
"It is futile for the U.S. to send anyone to show so-called support for Taiwan," Chinese Foreign Ministry spokesman Wang Wenbin said at a press briefing, according to state-run news agency Xinhua.
Wang cautioned that Washington should "prudently handle Taiwan-related issues so as not to further seriously damage the overall situation of China-U.S. relations and peace and stability in the Taiwan Strait."
Over the past several months, Beijing has ratcheted up military provocations with frequent flights through Taipei's air defense zone and gestures such as beach landing drills in a nearby province.
Washington does not maintain formal diplomatic relations with Taipei, but the two sides have been tightening economic and security ties as the United States looks to bolster its regional presence in the wake of an increasingly assertive China.
On Saturday, the U.S. Navy sent a missile destroyer through the Taiwan Strait as part of regular operations that Beijing routinely decries as provocative.
White House Indo-Pacific policy coordinator Kurt Campbell said on Monday that the visit by the delegation was meant to "underscore a consistent message of enduring support to maintain peace and stability."
"You will see over the course of the next several months a determination to sustain high-level engagement in the Indo-Pacific with presidential travel," Campbell said at an online event held by Washington-based think tank The German Marshall Fund.
While maintaining that it supports the principle of national sovereignty, Beijing has not condemned Russia for the invasion and has spoken out against the Western-led sanctions being imposed on Moscow.
The two countries had been pursuing closer ties ahead of the invasion, with Russian President Vladimir Putin making a rare trip abroad last month to meet with Chinese President Xi Jinping at the Winter Olympics. The leaders had a lengthy meeting and issued a joint statement declaring "no limits" to their cooperation.
Taipei has joined the sanctions against Russia, and on Tuesday confirmed it would participate in the ban against some Russian banks from using the SWIFT international payment system. The country also sent a shipment of 27 tons of medical supplies to Ukraine, its foreign ministry announced Tuesday.
Mullen's delegation includes Meghan O'Sullivan, former deputy national security adviser under President George W. Bush, and Michele Flournoy, a former Under Secretary of Defense in President Barack Obama's administration.
Their visit overlaps with a previously announced trip by former Secretary of State Mike Pompeo, who will arrive on Wednesday and is also scheduled to meet with President Tsai.
