The United States on Friday announced a $1.1 billion arms package for Taiwan and vowed to further strengthen the island’s defenses as tensions rise with Beijing, which Washington warned of “countermeasures.”

The sale comes a month after House Speaker Nancy Pelosi defiantly visited the self-governing democracy, prompting mainland China to launch a show of force that could be a dry run for a future invasion.

The package — the largest for Taiwan approved under President Joe Biden’s administration — includes $665 million to support contractors to maintain and upgrade a Raytheon radar early warning system that has been in operation since 2013 and Taiwan before would warn of an impending attack.

Taiwan will also spend around $355 million to buy 60 Harpoon Block II missiles, which can track and sink incoming ships if China launches a water attack.

The weapons also include $85.6 million for more than 100 Sidewinder missiles, a mainstay of Western militaries for their air-to-air firepower.

The announcement comes a day after Taiwanese forces shot down an unidentified commercial drone amid a sudden spate of mysterious incursions that have unsettled the island after Beijing’s earlier show of force, which said it had launched ballistic missiles over the capital Taipei.

China called Taiwan an “inalienable” part of its territory and urged the United States to “immediately revoke” the arms sales.

“It sends false signals to the ‘Taiwan Independence’ separatist forces and seriously jeopardizes China-US relations and cross-strait peace and stability,” said Liu Pengyu, spokesman for the Chinese Embassy in Washington.

“China will resolutely take legitimate and necessary countermeasures as the situation develops,” he said.

A spokesman for the State Department, which approved the sale, said the package is “essential to Taiwan’s security” and stressed that the United States still only recognizes Beijing and not Taipei.

“We urge Beijing to stop its military, diplomatic and economic pressure on Taiwan and instead engage in meaningful dialogue with Taiwan,” the spokesman said.

The sales “are routine cases in support of Taiwan’s ongoing efforts to modernize its armed forces and maintain a credible defense capability,” the spokesman said, on condition of anonymity as required by the protocol.

“The United States will continue to support peaceful resolution of cross-strait issues that meet the wishes and best interests of the people of Taiwan,” he said.

The sale is subject to US Congressional approval, which is virtually assured as Taiwan enjoys strong cross-party support.

Ahead of Pelosi’s visit, who is second only to the White House, Biden officials quietly argued with China that she does not represent government policy because Congress is a separate and equal branch of government.

In contrast, the weapons certification is clearly from the Biden administration, although consistent with sales since 1979, when the United States switched recognition to Beijing but agreed to maintain Taiwan’s ability to defend itself.

Biden appeared to break with decades of US policy on a trip to Tokyo in May by saying the United States would directly defend Taiwan if attacked, although his aides later retracted his comments and insisted that US politics remained ambiguous.

China views Taiwan as a province awaiting reunification, if necessary by force. China’s nationalists set up a rival government in Taiwan in 1949 after losing the mainland’s civil war, though the island has since blossomed into a vibrant democracy and a major technology hub.

Russia’s invasion of Ukraine has raised growing questions about whether China can follow suit in Taiwan and whether the island is prepared to defend itself.

Speaking in July, CIA chief Bill Burns said Chinese President Xi Jinping was still determined to take control of Taiwan, but that Russia’s problems in Ukraine may have prompted Beijing to wait and make sure there was a has overwhelming military advantage.