BEIJING (AFP, REUTERS) - China expressed "strong dissatisfaction" on Tuesday (Sept 25) over US plans to sell a batch of military parts to the self-governing island of Taiwan, adding to tensions between the global superpowers.

The US$330 million (S$450.7 million) contract would see the US ship standard spare parts for several aircraft including the F-16 fighter and the C-130 cargo plane, the State Department said in a statement on Monday.

China lashed out at the deal, saying it "severely violates" international laws and norms governing foreign relations, and expressed "strong dissatisfaction and firm opposition" to the sales.

Beijing sees Taiwan as part of its territory awaiting unification, and is deeply suspicious of the island's relations with the US.

Chinese foreign ministry spokesman Geng Shuang told a regular press briefing that Beijing has lodged "solemn representations" - an official protest - with the United States.

"We urge the US side to... immediately withdraw this armed sales plan and stop military contact with Taiwan lest it should cause severe damage to US-China relations, cross-straits stability and peace, and our cooperation in other important areas," he said.

Congress has 30 days to raise objections to the sale, though this is unlikely given the State Department has determined Taiwan continues to be "an important force for political stability, military balance, and economic progress in the region."

Washington remains Taipei's most powerful unofficial ally and its main arms supplier despite switching diplomatic recognition to Beijing in 1979.

China has stepped up diplomatic and military pressure on Taiwan since the Beijing-sceptic President Tsai Ing-wen took office two years ago, including staging a series of military exercises near the island.

Taiwan on Tuesday welcomed the US announcement, saying it would help the island strengthen its defence capabilities.

"As Taiwan faces gradually heightened threats, the US arm sales would... also boost Taiwan's confidence in strengthening self-defence to help maintain peace and stability in the Taiwan Strait," the foreign ministry said in a statement.

Taiwan's presidential office said the island's government would continue to increase its defence investment and "maintain close communication and cooperation" with the US on security issues.

Beijing has been incensed by recent warming ties between Washington and Taipei, including the approval by the US State Department of a preliminary licence to sell submarine technology to the island.

The US recently sanctioned a Chinese military procurement organisation, drawing a sharp protest from Beijing and a decision to postpone planned military talks.

Beijing and Washington are also at odds over China's wooing of Taiwan's diplomatic allies.

The new arms sale was announced on the same day that President Donald Trump's administration enacted new tariffs against China covering another US$200 billion of Chinese imports.

The move brings the amount of Chinese goods hit by duties to more than US$250 billion, roughly half of China's US exports.

US navy ship reportedly denied Hong Kong port visit

Separately, the US consulate in Hong Kong said China had denied a request for a US warship to visit the city.

The amphibious assault ship Wasp had been due to make a port call in the former British colony of Hong Kong in October, diplomatic sources said.

"The Chinese Government did not approve a request for a US port visit to Hong Kong by the USS Wasp," a consulate spokesman said. "We have a long track record of successful port visits to Hong Kong, and we expect that to continue," she added.

Asked whether China had denied the request, Geng did not directly respond to the question.

"For requests for US military ships to visit Hong Kong, China has always carried out approvals case by case, in accordance with the principle of sovereignty and the detailed situation," he told reporters, without elaborating.

In 2016, at a time of heightened tension over its territorial claims in the disputed South China Sea, China denied a request for a US carrier strike group led by the John C. Stennis to visit Hong Kong.

On Saturday, China summoned the US ambassador in Beijing and postponed joint military talks in protest against a US decision to sanction a Chinese military agency and its director for buying Russian fighter jets and a surface-to-air missile system.