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

In Trump’s first remarks since Iran rejected direct negotiations with Washington last week, he told NBC News that U.S. and Iranian officials were talking, but did not elaborate.

“If they don’t make a deal, there will be bombing,” Trump said in a telephone interview. “It will be bombing the likes of which they have never seen before.”