SAN SALVADOR (Reuters) – El Salvador’s vice president on Tuesday accused Mexico of leaving Central America out of talks with the United States over measures to stem the flow of migrants headed north, and using the region as a negotiating tool to reach a deal.

Mexico struck the pact last week under pressure to avert import tariffs of 5% on its goods, which U.S. President Donald Trump had vowed to impose unless the neighboring nation did more to curb migration.

As part of the deal, Mexico said it would deploy its National Guard security force to its southern border with Guatemala, as well as take in people seeking asylum in the United States while their cases are adjudicated.

Mexican officials also called on other countries with high migrant flows, including those in Central America, to share in its responsibility to slow migration to the United States.

El Salvador’s Vice President Felix Ulloa said Mexico had been forced to make concessions under threat of a trade war, and did not take into account his country’s stance.

“Mexico has only negotiated bilaterally, but has suggested that Central America is on board. We’re practically a bargaining chip in these negotiations,” Ulloa said at a public event.

“We know that we’re in an extremely delicate moment for the U.S. administration’s policy, which currently has been defined along with the Mexican state, and which will definitely affect migrant populations.”

A document held by Trump on Tuesday, which he said contained details of the pact with Mexico, laid out a “regional approach to burden-sharing in relation to the processing of refugee status claims to migrants.”

U.S. Vice President Mike Pence has suggested also Guatemala could receive asylum seekers from its neighbors, which include El Salvador.