Beijing on Thursday strongly condemned and firmly rejected the visit of United States Congress officials to China's Taiwan region, saying it violated the one-China principle and broke the US promise to only maintain non-official relations with the island.

A delegation of US bipartisan House lawmakers, led by Stephanie Murphy, a Democrat from Florida who sits on the House Armed Services Committee, arrived in Taiwan on Wednesday.

The visiting Congressmen met with Taiwan leader Tsai Ing-wen and will stay until Friday.

The group was the latest in a string of senior officials from the US to visit the island since early August.

"China urges the US to immediately stop any official ties with Taiwan and not send any wrong signals to the 'Taiwan independence' separatist forces," Foreign Ministry spokeswoman Mao Ning told a daily news briefing.

Mao reiterated that there is only one China in the world and Taiwan is an inalienable part of China's territory, adding that the government of the People's Republic of China is the sole legal government representing the whole of China.

Mao urged relevant US politicians to abide by the one-China principle and the three China-US joint communiques.

"China will not waver in opposing 'Taiwan independence' separatist activities and external interference," she vowed, noting China would continue to firmly safeguard its sovereignty and territorial integrity.

Earlier reports said that the US and Taiwan would soon start formal talks on a trade and economic initiative that was unveiled in June.

During talks with her US guests, Tsai expressed confidence that Taiwan and the US could reach a high-standard trade agreement through the initiative.

In response, Murphy told Tsai she supported such an agreement.