HONG KONG — The White House on Thursday accused China of “apparent interference” in El Salvador’s domestic politics after the Central American nation established diplomatic ties with Beijing this week.

The statement also sharply criticized El Salvador, saying the United States would re-evaluate its relationship with the country.

The Trump administration’s comments are its strongest pushback to date on China’s efforts to curb the international recognition of Taiwan, the self-ruled democracy Beijing claims as part of its territory. They also reflect a growing unease about China’s growing influence in a region where the United States has long been the dominant force.

El Salvador severed ties with Taiwan on Tuesday, leaving Taiwan with just 17 formal diplomatic partners. China has stepped up its campaign to woo Taiwan’s diplomatic partners since Tsai Ing-wen was elected Taiwan’s president in 2016, replacing a more pro-Beijing leader.

The White House comments were far sterner than those made by the State Department after other countries in the region, including Panama and the Dominican Republic, switched ties from Taiwan to China.

It accused El Salvador’s government of making the decision, which “affects not just El Salvador, but also the economic health and security of the entire Americas region,” without transparency months before an election.

“The El Salvadoran government’s receptiveness to China’s apparent interference in the domestic politics of a Western Hemisphere country is of grave concern to the United States, and will result in a re-evaluation of our relationship with El Salvador,” it said.

The White House’s toughened its tone toward countries that have shifted recognition from Taiwan to China this summer after Burkina Faso made the switch in May.

“Previously it was unusual for the U.S. government to make such remarks, if for no other reason that the U.S. itself made this switch in 1979,” said Ross Darrell Feingold, a Taipei-based consultant who advises on political risk in Asia.

Taiwan’s embassy in San Salvador. El Salvador’s decision to cut ties leaves the Taipei government with just 17 formal diplomatic partners.CreditMarvin Recinos/Agence France-Presse — Getty Images

When the United States established formal ties with the People’s Republic of China in 1979, it ceased formal relations with Taiwan. But the United States maintains a robust informal relationship with Taiwan, and recently unveiled a $250 million complex in its capital, Taipei, that serves as a de facto embassy.

The stronger U.S. tone likely reflects the influence of John R. Bolton, a staunch Taiwan defender who became President Trump’s national security adviser in April, Mr. Feingold said.

“Bolton has a long record of support for Taiwan, including changes to the traditional approaches to the trilateral U.S.-China-Taiwan relations, so it is no surprise that we are seeing something different by way of a U.S. response to China’s actions that reduce Taiwan’s international space,” he said.

The government of El Salvador, which is led by a party of former leftist guerrillas, has also been a frequent target of Republican critics.

Senator Marco Rubio of Florida said this week that he had spoken with President Trump about ending American aid to El Salvador after it established formal ties with Beijing, and he would join with a fellow Republican, Senator Cory Gardner of Colorado, to carry that out.

Mr. Gardner told Reuters on Thursday that he would introduce legislationthat would enable the State Department to use aid and other levers to encourage countries to maintain Taiwan ties.

Mr. Rubio wrote on Twitter that there “would be real consequences in our relationship with #ElSalvador if they broke with #Taiwan in favor of #China. They think we are going to react the same way we did to #Panama & #DominicanRepublic. They are very wrong.”

In January the Trump administration canceled a program that allowed 200,000 Salvadorans to temporarily live in the United States. That move prompted criticism that it would destabilize a country struggling with high levels of street crime.

President Trump has shown before that he is willing to shake up the traditional framework of ties between the United States, China and Taiwan. In December 2016, before he had assumed office, he took a congratulatory call from President Tsai, breaking with decades of precedent. He later said in a phone call with China’s president, Xi Jinping, that he would abide by the “One China policy,” under which the United States does not formally recognize the government of Taiwan.

Taiwan’s foreign minister, Joseph Wu, said Friday he was not worried that Taiwan could be used as a pawn of the United States in the current trade dispute with China.

“We understand Washington D.C.’s support of Taiwan continues to be very strong,” Mr. Wu told Bloomberg. “Taiwan is a positive element in the U.S. economy and I just don’t worry that Taiwan is going to become a chip to be negotiated with by the U.S.”