WASHINGTON, United States — US President Donald Trump said Friday he was sending a second aircraft carrier group to the Middle East -- warning it would be a "bad day for Iran" if it fails to make a deal on its nuclear program.

 

Trump has upped the military threat against the Islamic republic in the wake of Tehran's deadly crackdown by security forces on protests last month that rights groups say killed thousands.

 

"In case we don't make a deal, we'll need it," Trump told journalists at the White House when asked about reports the USS Gerald R. Ford would be moved from the Caribbean to the Middle East.

 

"It'll be leaving very soon. We have one out there that just arrived. If we need it we'll have it ready, a very big force."

 

Trump said he believed the talks with Iran would be "successful" but added: "If they're not, it's going to be a bad day for Iran, very bad."

 

The US leader had already sent one aircraft carrier, the USS Abraham Lincoln, to the Middle East, as part of a fleet of 12 US Navy ships in the region.

 

The four vessels led by the Ford, the world's largest aircraft carrier, have been in the Caribbean, where US forces captured Venezuelan president Nicolas Maduro in January.

 

They are not expected to return to their home ports until late April or early May, The New York Times said.

 

'Terribly difficult'

 

While the protests have subsided for now, US-based Reza Pahlavi, the son of the shah ousted by the 1979 Islamic revolution, urged Iranians to chant slogans against the clerical establishment in the coming days to coincide with demonstrations abroad.

 

Rather than pointing to the crackdown -- which has seen tens of thousands arrested and hundreds facing possible execution, according to rights groups -- Trump has recently focused his military threats on Iran's nuclear program.

 

The West fears the program is aimed at making a bomb, which Tehran denies.

 

The head of the UN nuclear watchdog, Rafael Grossi, said Friday that reaching an accord with Iran on inspections of its processing facilities was possible but "terribly difficult".

 

Iran and the United States, who have had no diplomatic relations since shortly after the revolution, held talks on the nuclear issue last week in Oman. No dates have been set for new talks yet.

 

The United States joined Israel's 12-day war against the Islamic republic in June, carrying out strikes on Iranian nuclear facilities.

 

Israeli prime minister Benjamin Netanyahu said after meeting Trump in Washington on Wednesday that the US leader believed he may clinch a "good deal".

 

But the Israeli prime minister himself expressed skepticism at the quality of any agreement if it didn't also cover Iran's ballistic missiles and support for regional proxies.