Taiwan’s President Tsai said the United States National Guard plans on a cooperation with Taiwanese military. The two countries have been working towards tightening security cooperation amid Taiwan’s complaints of a rising threat from China.

Although the U.S. has been Taiwan’s most important international backer and arms provider, there’s no formal diplomatic relations between the two. China has been increasing its military presence near the island in recent years to assert its sovereignty claims.

Last week China’s military, the People’s Liberation Army (PLA), said it had conducted military exercises near the island as a warning to Taiwan against its “collusion” with the U.S.

China’s move came after Biden’s announcement that the U.S. would get involved militarily if China were to attack Taiwan. While Biden’s announcement was considered as a signal of policy change, the U.S. officials said there were no policy change.

In her meeting with visiting U.S. Senator Duckworth, who is also a retired Army National Guard lieutenant colonel, Tsai noted that Duckworth was one of the main sponsors of Taiwan Partnership Act, which has received bipartisan support in the Congress but yet to become law.

Tsai said, without giving details, the U.S. Department of Defense was planning a cooperation between the National Guards and Taiwan’s military.

It has been reported that the U.S. could commit Hawaii’s National Guard for the program.

Duckworth said the primary reason of her visit was to reiterate U.S. support for Taiwan, and that there was a big support for the island from the U.S. Congress.

Nevertheless, Taiwan was not included in the U.S.’ Indo-Pacific Economic Framework last week despite its lobbying efforts.

Tsai said Taiwan will keep expressing its willingness to participate.