U.S. President Joe Biden said Tuesday he has spoken to Chinese President Xi Jinping about Taiwan and they agreed to abide by the Taiwan agreement, as tensions have flared up between Taipei and Beijing.

"I've spoken with Xi about Taiwan. We agree ... we'll abide by the Taiwan agreement," he said. "We made it clear that I don't think he should be doing anything other than abiding by the agreement."

Biden appeared to be referring to Washington's long-standing "one-China policy" under which it officially recognizes Beijing rather than Taipei, and the Taiwan Relations Act (TRA), which makes clear that the U.S. decision to establish diplomatic ties with Beijing instead of Taiwan rests upon the expectation that the future of Taiwan will be determined by peaceful means.

The comments to reporters at the White House – made after Biden's return from a trip to Michigan touting a spending package – come amid escalations in the Taiwan-China relationship.

China claims Taiwan as its own territory, which should be taken by force if necessary. Taiwan says it is an independent country and will defend its freedoms and democracy, blaming China for the tensions.

Taiwan has reported 148 Chinese air force planes in the southern and southwestern part of its air defense zone over a four-day period beginning Friday, the same day China marked a key patriotic holiday, National Day. The United States urged China on Sunday to stop its military activities near Taiwan.

"The United States is very concerned by the People's Republic of China's provocative military activity near Taiwan, which is destabilizing, risks miscalculations and undermines regional peace and stability," State Department spokesperson Ned Price said in a statement Sunday, according to remarks carried by Reuters.

Biden also appeared to be referencing a 90-minute call he held with Xi on Sept. 9, their first talks in seven months, in which they discussed the need to ensure that competition between the world's two largest economies does not veer into conflict.

Meanwhile, a group of French senators arrived in Taiwan for a five-day visit Wednesday, following the Chinese show of force. The group, led by senator Alain Richard, will meet with President Tsai Ing-wen, Taiwanese economic and health officials and the Mainland Affairs Council.

Richard, a former French defense minister, previously visited Taiwan in 2015 and 2018, according to Taiwan's semi-official Central News Agency, and heads the Taiwan Friendship group in the French senate.

China's ambassador to France Lu Shaye sent a warning letter in February calling on Richard to cancel the Taiwan visit, according to local media reports.

The visit will likely provoke a rebuke from China, which claims self-ruled Taiwan as its own territory and therefore opposes any international engagement with the island such as visits by foreign government officials. It also has aggressively poached Taiwan’s remaining diplomatic allies.

China and Taiwan split amid civil war in 1949. Today they have extensive trade and investment ties but no official relations, and China has increasingly mobilized military, diplomatic and economic pressure to undermine Tsai's independence-leaning administration.