Iran’s president says Tehran has rejected direct negotiations with the United States in response to a letter from President Donald Trump over its rapidly advancing nuclear program.

Mexican Foreign Minister Juan Ramon de la Fuente spoke with the U.S. Deputy Secretary of State Christopher Landau on Wednesday in a call focused on strengthening bilateral relations, Mexico's foreign ministry said.

American and Iranian officials are "talking," the president said, following reports that Tehran had rejected a negotiation proposal.

President Donald Trump threatened Iran with bombings and secondary tariffs if the country does not come to an agreement with his administration about its nuclear program. “If they don’t make a deal, there will be bombing,” Trump said during a phone call with NBC News’ Kristen Welker on Sunday.

Donald Trump has issued his biggest threat against Iran, warning of ‘bombing the likes of which they have never seen before’. Why? It’s the US president’s latest attempt of getting Tehran to the negotiating table over the nuclear deal,

"In this response, although direct negotiations between the two parties are rejected, it has been stated that the path for indirect negotiations is open," Iran said.

The statement marks the first official acknowledgment from Iran about its response to a letter sent by President Donald Trump.

Anticipation and concern is growing for the major new tariffs President Donald Trump says he’ll announce by mid-week. Uncertainty still surrounds Trump’s trade plans, which he has announced and then reversed in the past.

Donald Trump threatened Iran with bombings and secondary tariffs if Tehran did not come to an agreement with Washington over its nuclear program.