China considers Taiwan part of its territory, not a sovereign political entity, and is threatening to use force to take control of the island.

China's foreign minister demanded on Tuesday that the United States stop interfering in the Taiwan issue, adding that Beijing retains the "option to act" if the island declares independence.

"We reserve the option to act if there is a circumstance that violates the law of the People's Republic of China against separatism," said Qin Gang, quoted by Lusa, at a press conference on the sidelines of the annual session of the National People's Assembly, China's highest legislative body.

"The determination of the Chinese people to defend their sovereignty cannot be underestimated," he stressed. "That is a red line that cannot be crossed."

The Chinese leader said that the US "must stop interfering in China's internal affairs". "Why don't you respect China's sovereignty on the Taiwan issue, but demand that we show respect for Ukraine's sovereignty?" he asked. "Why are they sending arms to Taiwan and asking us not to send arms to Russia?".

"If the US wants peace, it must stop using Taiwan to contain China and reject and prevent Taiwanese independence," he said.

When answering a question about Taiwan, Qin opened a copy of the Constitution of the People's Republic of China, citing that the island is "sacred territory".

"Separatism in Taiwan is not compatible with peace. The threat is secessionism. And if the United States doesn't change its attitude, ties with China could be seriously damaged," he said.

"It's China's business, period. It's not something that other countries have to evaluate. Some US authorities say otherwise, we reject that and we're paying attention," he added.

At the opening of the plenary session of the National People's Assembly last Sunday, outgoing Premier Li Keqiang promised that China will "resolutely fight" against Taiwan's "independence" and "for the reunification of the motherland".

China considers Taiwan part of its territory, rather than a sovereign political entity, and is threatening to use force to take control of the island. The territory is also a source of tension between Beijing and Washington, Taipei's main ally and arms supplier.