Beijing warns Washington of "serious consequences" for its support for "separatist forces" in Taiwan amid US Senator Tammy Duckworth's visit to the island, Chinese Foreign Ministry spokesperson Zhao Lijian said on Wednesday.

Senator Duckworth is the chair of the US Senate Armed Services Subcommittee on Airland. She arrived in Taiwan on Monday for a three-day visit as part of a tour in the Indo-Pacific region and met with President Tsai Ing-wen on Tuesday. It was her second visit to Taiwan this year.

Following Duckworth's meeting with the Taiwanese president, Zhao told a press briefing that his country strongly opposed the visit and urged the United States to "earnestly abide by the one-China principle and the three China-US joint communique" and refrain from "sending any wrong signals to the 'Taiwan independence' separatist forces."

"I clearly conveyed China's position regarding the visit of the said US senator to Taiwan yesterday. I would like to stress that the main reason for the current tensions in the Taiwan Strait is that the Taiwanese administration is using the US to achieve independence, and some people in the US are using Taiwan to deter China," the Chinese diplomat added.

He also accused the United States of "openly inciting and supporting" separatist forces in Taiwan and saying one thing while doing the opposite, something that could jeopardize Taiwan as the US itself "could face serious consequences."

The Taiwanese Ministry of National Defense said Monday that Beijing had sent some 30 warplanes near the island. The spokesperson for the Eastern Theater Command of the Chinese Army later explained that Beijing had carried out a joint air and sea policing mission near the island as a response to the collusion between Washington and Taipei.

China sees Taiwan as an inalienable part of its sovereign territories, being very vocal about its opposition to any official contact between Taipei and other nations. 

The United States, on the other hand, has provided Taiwan with numerous weapon systems and supported pro-independence elements there.

Beijing's foreign ministry has reiterated on numerous occasions that the one-China principle was a political foundation of US-Sino relations, explaining that the US violated its own obligations has been jeopardizing bilateral cooperation as well as peace and stability in the region.

Despite having stated that the US will not change its policy regarding China, President Joe Biden angered Beijing by appearing to signal a change in the US policy of "strategic ambiguity" on Taiwan. In a contradictory statement, Biden noted a week ago that "We agreed with the One China policy, we signed on to it... but the idea that (Taiwan) can be taken by force is just not appropriate," as the One China policy states that Taiwan is a part of the sovereign mainland.

Earlier, during a phone call between National Security Advisor Jake Sullivan and Chinese Director of the Office of the Central Commission for Foreign Affairs Yang Jiechi, the latter said China would take drastic measures to protect its sovereignty and national interests if the US interferes in the country's internal affairs.

Washington, according to Yang, made a series of "incorrect actions and statements interfering in China's internal affairs and damaging its national interests."