WASHINGTON (Reuters) - A leading U.S. Republican senator said Thursday he is preparing legislation to discourage Taiwan’s few remaining allies from switching their allegiance to China, after El Salvador became the third country this year to move toward Beijing.

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Senator Cory Gardner, chairman of the Foreign Relations Committee’s Asia subcommittee, told Reuters he will introduce within a few days a measure encouraging countries to stick with Taipei.

Among other things, he said the measure would authorize the State Department to take action such as downgrading relations or altering foreign assistance to discourage decisions seen as adverse for Taiwan.

“The Taipei Act of 2018 would give greater tools and directions to the State Department in making sure we are as strong a voice as possible for Taiwan,” Gardner told Reuters in a telephone interview.

It would require a U.S. strategy to engage with governments around the world to support Taiwan’s diplomatic recognition or unofficial ties. It also would authorize State to downgrade U.S. relations, or suspend or alter U.S. foreign assistance, including foreign military financing, to governments that take adversarial actions with regard to Taiwan.

He stressed that the bill would not mandate action against countries that have chosen diplomatic relations with Beijing.

“This is a permissive bill,” he said. “It’s something that gives one more tool in the bundle of tools to address Chinese bullying.”

On Tuesday, the State Department said the United States was “deeply disappointed” by El Salvador’s decision and was reviewing its relationship with San Salvador, without elaborating further.

Washington does not recognize Taipei diplomatically but considers it a staunch ally in the Pacific Rim. Several members of Congress, who see Beijing as a threat to U.S. security and international influence, have expressed frustration with what they see as President Donald Trump’s failure to adopt a strategy for Taiwan.

A legislative effort to boost Taiwan, which would anger China, comes as Washington and Beijing have escalated an acrimonious trade war. On Thursday, the world’s two biggest economies implemented punitive 25 percent tariffs on $16 billion worth of each other’s goods.

Taiwan now has formal relations with only 17 countries, many of them small, less developed nations such as Belize and Nauru.

Gardner met last week with Taiwanese President Tsai Ing-wen about what Congress could do to support Taiwan.

The senator said he had spoken to several Democratic senators, hoping to build bipartisan backing necessary for his bill to pass the chamber. He said he also planned to work with members of the House of Representatives and the White House.

China has claimed sovereignty over Taiwan since the 1940s, although both sides have been self-ruled since then. Beijing considers Taiwan a wayward province of “one China,” ineligible for state-to-state relations, and has never renounced the use of force to bring the island under its control.