Capitol Hill correspondent Katherine Gypson and VOA Persian's Katherine Ahn contributed to this report from Washington.
The United States was "cocked & loaded," ready to strike three sites in Iran in retaliation for the downing of a U.S. drone over the Strait of Hormuz but called off the attacks at the last possible moment to spare Iranian lives.
The revelation by U.S. President Donald Trump on social media Friday followed news reports that the president initially authorized strikes on a handful of Iranian targets, such as radar installations and missile batteries, before pulling back.
"We were cocked & loaded to retaliate last night on 3 different sights when I asked, how many will die. 150 people, sir, was the answer from a General. 10 minutes before the strike I stopped it," Trump tweeted, saying the action would have been disproportionate.
"I am in no hurry," Trump added.
The president also said that he authorized additional "biting" sanctions against Iran late Thursday night as part of his administration's maximum pressure campaign to force Iran to restart negotiations over its nuclear program.
"Iran can NEVER have Nuclear Weapons, not against the USA, and not against the WORLD!" Trump tweeted.
The move appears to pull Washington and Tehran back from the brink of armed conflict that could engulf the Middle East. President Trump spoke Friday with Saudi Arabian Crown Prince Mohammed bin Salman.
"The two leaders discussed Saudi Arabia's critical role in ensuring stability in the Middle East and in the global oil market," said White House spokesperson Hogan Gidley. "They also discussed the threat posed by the Iranian regime's escalatory behavior."
U.S. House Speaker Nancy Pelosi said Friday, "We are in an extremely dangerous and sensitive situation with Iran. We must calibrate a response that de-escalates and advances American interests, and we must be clear as to what those interests are." She added that any hostilities against Iran must first be approved by Congress.
Concern about a potential armed confrontation between the U.S. and Iran has been growing since U.S. officials recently blamed Tehran for mine attacks on two oil tankers in the Strait of Hormuz, allegations Tehran denies, and Iran's downing of an unmanned U.S. drone this week.
James Phillips, a senior researcher at the conservative Washington-based Heritage Foundation, said he believes the immediate risk of a U.S.-Iran conflict has passed.
"It's probably over as far as the incident goes with the shoot down of the drone. But, I think if there are further provocations, the president will respond in a strong and effective manner," he said in a VOA Persian interview.
Phillips also said he does not expect Tehran to accept U.S. calls for negotiations while Trump continues a "maximum pressure campaign" of sanctions on Iran.
"I doubt that Tehran will be serious until it sees who wins the next presidential election," he said.
The U.S. announced this week it was authorizing another 1,000 troops, including a Patriot missile battery and additional manned and unmanned reconnaissance aircraft, to bolster defenses at U.S. positions in Iraq and Syria.
Trump earlier said the unmanned surveillance drone that was shot down was flying over international waters in the Strait of Hormuz when it was hit by an Iranian missile, and said the incident was a "very bad mistake."
Iran says the drone flew into its air space, a "blatant violation of International law."
Friday, the head of Iran's Revolutionary Guard, General Amir Ali Hajizadeh, showed off pieces of wreckage he said Iran had recovered after shooting down the U.S. drone.
He also said Iran itself had shown restraint, opting not to shoot down another U.S. plane, sparing American lives.
"Another spy aircraft called P8 was flying close to this drone," Hajizadeh said. "That aircraft is manned, and has around 35 crew members, well we could have targeted that plane."
"It was our right to do so, and yes it was American, but we didn't do it," he said.
U.S. Air Forces Central Command, which oversees U.S. military activity in the region, has called many of the Iranian claims "categorically false."
Central Command spokesman Lt. Col. Earl Brown rejected Iran's claims that a surveillance plane was flying alongside the drone, saying, "At no point in time did any U.S. aircraft enter Iranian airspace on June 19."
The U.S. Defense Department has also released images to bolster its assertion the drone did not enter Iranian airspace. But a news report said the department erroneously labeled the drone's fight path the location where it was shot down. An image apparently showing the airborne drone exploding provided little context.
"It's a really dangerous game and if I was flying in that region, which I have before, I'd be a little more nervous," Rep. Adam Kinzinger, a Republican member of the House Foreign Affairs Committee and a U.S. Air Force Veteran who flew missions in Iraq and Afghanistan, told reporters Friday.
Kinzinger said Iran has moved the situation "this time - and multiple times prior - into the kinetic military realm. This is not the president doing it. I think a military response, even a small one is appropriate but if there's a strong economic cost then I think that could work, too."
But in recent days, Democrats have expressed concern Trump has not adequately consulted with the U.S. Congress on a military response they say could have grave consequences.
"I think every president would probably say initial, retaliatory strikes are ok but let's de-escalate this, let's look for a diplomatic solution," Rep. Ami Bera, a member of the House Foreign Affairs Committee, told VOA. "He (Trump) may be walking right into the hands of what the Revolutionary Guards want."