WASHINGTON (Reuters) - The United States is “deeply disappointed” by El Salvador’s decision to break diplomatic ties with Taiwan in favor of China and is reviewing its relationship with San Salvador as a result, a spokesman for the U.S. State Department said on Tuesday.

FILE PHOTO - A man waits to visit the Taiwan embassy a day after the Salvadoran government announced that it has broken off diplomatic relations with Taiwan, in San Salvador, El Salvador August 21, 2018. REUTERS/Jose Cabezas

El Salvador on Monday became the third Latin American country in the past two years to switch allegiances from Taipei to Beijing and said attracting investment and developing the economy were key goals behind the decision.

“Although we recognize the sovereign right of every country to determine its diplomatic relations, we are deeply disappointed by this decision,” said a spokesman for the U.S. State Department, who did not want to be identified by name.

“We are reviewing our relationship with El Salvador following this decision,” he said.

The official did not elaborate.

The U.S. ambassador in El Salvador, Jean Manes, posted on Twitter earlier that the United States was analyzing the “worrisome” decision and that it would impact relations between the two countries. She also did not elaborate.

U.S. relations with El Salvador have been strained over President Donald Trump’s threats to cut aid from countries that “do nothing” to stop MS-13 gang members from crossing illegally into the United States.

Manes said at an event on Tuesday Salvadorans should demand transparency about how their government resolved to swap diplomatic partners.

“I think you should know, exactly, all the details of the negotiation,” she said.

The United States, which is currently locked in a major trade dispute with China, its main strategic rival in Asia, also has formal diplomatic relations with Beijing, rather than Taipei. However, it is required by law to help Taiwan with self-defense and is the island’s primary source of weapons.

The State Department official said China’s efforts to unilaterally alter the status quo with Taiwan were harmful and “undermine the framework that has enabled peace, stability, and development for decades.”

“The United States urges China to abstain from coercion that would jeopardize the security, or the social or economic system, of the people on Taiwan,” he said. Taiwan was a democratic success story, a reliable partner, and a force for good in the world, the official said.

“The United States will continue to support Taiwan as it seeks to expand its already significant contributions to addressing global challenges, and as Taiwan resists efforts to constrain its appropriate participation on the world stage,” he said.

Taiwan President Tsai Ing-wen said on Monday the island would not bow to pressure after she made a high-profile trip to Latin America last week that included stops in the United States, which drew criticism from China.

In March, Trump signed legislation that encourages the United States to send senior officials to Taiwan to meet Taiwanese counterparts and vice versa.

While Tsai was not invited to the United States for an official visit last week, she met U.S. senators while she was there, attended banquets with overseas Taiwanese and spoke of the need for strong ties with Washington.