US President Trump on Friday said he is hopeful U.S. negotiations with Iran on its nuclear program will be successful, but warned that if they fail, it would be a “bad day” for Tehran, APA reports citing The Hill.

As the U.S. builds up its defense forces in the Middle East, the Trump administration is also negotiating with the Islamic Republican about its nuclear program. Trump reiterated his preference for letting the talks continue but also offered a stern warning when asked if he believed the talks would succeed.

“I think they’ll be successful. And if they’re not, it’s going to be a bad day for Iran, very bad,” Trump told reporters at the White House ahead of his trip to Fort Bragg to honor military members involved in the Venezuela operationthat captured ex-leader Nicolás Maduro.

Trump said a second aircraft carrier he ordered to the Middle East would be leaving soon in the event it would be needed should talks collapse.

“We have one out there that just arrived. If we need it, we’ll, well, we have it ready,” he said.  “A big, a very big force.”