The United States has approved a $100m support contract with Taiwan aimed at boosting the island’s missile defence systems amid heightened tensions with China.

The funds would be used to “sustain, maintain, and improve” the self-ruled island’s Patriot missile defence system, the Pentagon said on Monday.

A statement from the US Defense Security Cooperation Agency (DSCA) said it had delivered the required certification notifying Congress following State Department approval for the sale, which was requested by Taiwan’s de facto embassy in Washington.

Upgrades to the Patriot Air Defense System would “help improve the security of the recipient and assist in maintaining political stability, military balance, economic and progress in the region”, the DSCA said in a statement.

“This proposed sale serves US national, economic, and security interests by supporting the recipient’s continuing efforts to modernize its armed forces and to maintain a credible defensive capability,” the agency said.

China claims Taiwan as its own and has been stepping up pressure on the island ever since Tsai Ing-wen was first elected president in 2016. Beijing has not ruled out the use of force to retake the island and has made repeated air sorties into Taiwan’s air defence zone.

Taiwan’s foreign ministry said it “highly welcomed” the US decision.

“In the face of China’s continued military expansion and provocative actions, our country will maintain its national security with a solid defence, and continue to deepen the close security partnership between Taiwan and the United States,” it said in a statement.

Taiwan’s defence ministry has said the decision to obtain newer Patriot missiles was made during a 2019 meeting with US officials in the administration of former US President Donald Trump.

The ministry said the deal was expected to “come into effect” within one month.

Like most countries, the US does not have formal relations with Taiwan, but Washington is bound by law to provide the island with the means to defend itself.

Tsai is working to modernise the Taiwan military to enhance its capacity for ‘asymmetric warfare‘, which is designed to make any Chinese attack more difficult and costly.