Stressing the importance of diplomacy, Deputy Defense Secretary Kathleen Hicks said on Friday that conflict was China was neither desirable nor inevitable.

In remarks to a virtual meeting of the Aspen Defense Forum, Hicks noted that China can challenge the United States in several categories.

She noted that Chinese military capability is advancing in fields including long-range missiles and air defense systems, as well as in cybersecurity and in space.

“Beijing has the economic, military and technological capability to challenge the international system and America’s interests within it,” she said, noting China’s claims of sovereignty in the South China Sea.

“Let there be no doubt, China presents a real and enduring challenge,” she added, saying that the support of the U.S. Congress is necessary to ensure that the Defense Department can deter Chinese aggression.

Hicks said, though, that open diplomatic channels with China are crucial, with the U.S. military prepared to “serve as a supporting player to diplomatic, economic and other goals.”

Tensions between China and the United States and its allies have been simmering for months.

This has been apparent in Chinese demonstrations of military air power near Taiwan, a U.S. ally China regards as a breakaway province, and also in regular transits of U.S. warships through the Taiwan Strait, which separates the island of Taiwan from the Chinese mainland.

On Friday, Chinese foreign ministry spokesman Wang Wenbin said that China is willing to put a stop to any movement toward Taiwanese independence, a day after U.S. Director of National Intelligence Avril Haines told the Senate Armed Services that Taiwan’s views of independence are “hardening” amid the tensions.

Last week, Navy Adm. Charles A. Richard, commander of U.S. Strategic Command, told the Senate Armed Services Committee that China is on pace to double its nuclear weapons stockpile by the end of the decade.

Richard added that China can mount its intercontinental ballistic missiles on trucks so their location can be concealed.

In the South China Sea, Chinese overflights to the edge of Taiwanese air sovereignty have been common, as have visits by U.S. warships and those of allies.

The Theodore Roosevelt Carrier Strike Group, comprised of the aircraft carrier USS Theodore Roosevelt and numerous escort destroyers and frigates, entered the sea to conduct routine operations earlier in April.