U.S. Secretary of State Antony Blinken told his Chinese counterpart on Sunday that the United States opposed actions by China that have increased tensions across the Taiwan Strait, a senior State Department official said.

During an hour-long meeting with Chinese Foreign Minister Wang Yi on the sidelines of a Group of 20 summit, Blinken made "crystal clear" that Washington opposes any unilateral changes by Beijing to the status quo there, the official said.

A recent increase in Chinese military exercises in Taiwan's air defence identification zone is part of what Taipei views as stepped-up military harassment by Beijing.

China claims the island as part of its own territory and views any foreign intervention over Taiwan as interference in its domestic affairs.

The United States wants to manage the intense competition between the world's two largest economies responsibly, the State Department official said, adding that both sides acknowledged that open lines of communication are paramount.

Blinken's meeting with Wang was their first in person since a fiery exchange in Anchorage, Alaska in March, when U.S. and Chinese officials leveled sharp rebukes of the others' policies in a rare public display.

Sunday's meeting in Rome was "exceptionally candid" but productive, and would help lay the groundwork for a virtual summit between U.S. President Joe Biden and Chinese President Xi Jinping later this year, the official said.

While the United States, like most countries, has no formal ties with Taiwan, Washington is the island's most important international backer and main arms supplier, and is required by law to provide it with the means to defend itself.

The United States has long followed a policy of "strategic ambiguity" on whether it would intervene militarily to protect Taiwan in the event of a Chinese attack, though Biden said last week that it would come to Taiwan's defense if necessary.

Blinken made clear that Washington had not changed its "one China" policy regarding Taiwan, the official said.

The top U.S. diplomat, who will next week attend the COP26 U.N. climate conference in Glasgow, urged China to fulfill its obligations as a responsible power in terms of limiting emissions, the official said.

He also raised concerns about other Chinese actions that "undermine the international rules-based order and that run counter to our values and interests," including in relation to human rights, Xinjiang, Tibet, Hong Kong, the East and South China Seas, the State Department said.

Blinken and Wang did not discuss a recent Chinese hypersonic weapons test that military experts say appears to show Beijing's pursuit of an Earth-orbiting system designed to evade American missile defenses, the official said.