Iran's foreign minister said on Thursday that Tehran was "prepared for the worst" and warned the United States against putting itself on "collision course" with his country.
On the sidelines of a news conference in the Libyan city of Benghazi, minister Ali Akbar Salehi was asked about news reports of Washington accelerating plans for a strike on Iran over its controversial nuclear programme.
"The US has unfortunately lost wisdom and prudence in dealing with international issues. It depends only on power.
"They have lost rationality; we are prepared for the worst but we hope they will think twice before they put themselves on a collision course with Iran," Salehi said.
Washington and other Western powers suspect Tehran is seeking to build nuclear weapons, a charge Iran denies. It says its nuclear programme is for purely peaceful ends to which it has a right.
Washington insisted on Wednesday that it remains committed to a diplomatic solution of the nuclear standoff with Iran as talk mounted in Israel of a political push for a pre-emptive strike.
"We remain focused on a diplomatic channel here, a diplomatic course in terms of dealing with Iran," White House spokesman Jay Carney said.
Earlier, at a joint news conference, Salehi was questioned about Nato’s military strikes in support of fighters battling to overthrow dictator Muammer Gaddafi.
"Nato did not come to help without any reason... they made mistakes. The president of Iran (Mahmoud Ahmadinejad) has criticised these mistakes," said Salehi.
Libyan leader, National Transitional Council chief Mustafa Abdel Jalil, responded: "Gaddafi troops tried to kill people on 19 March.
"If it were not for Nato, there would have been a massacre by Gaddafi troops. Libyan fighters brought victory on the ground but we must not forget the coalition's air strikes that supported and helped us."
On the fate of revered, Iranian-born, Lebanese Shiite leader Musa Sadr, who disappeared in 1978 on a trip to Libya, Abdel Jalil said: "One of the priorities of the new government is to investigate what Gaddafi did to the Libyan people and people from different nations."
Once the inquiry was complete, Libya would give details to both the Iranian and Lebanese governments, he said.
Abdel Jalil told reporters that he and Salehi did not discuss the issue of Syria. Libya has supported the opposition movement trying to oust the Syrian leadership while Iran has backed President Bashar Al Assad.
"Every country has the right about whom to support," Jalil said.