President Trump pulled the United States out of the nuclear deal with Iran a year ago.
Russian President Vladimir Putin warned the US against retaliating for the incident, saying USA use of force against Iran "would be a disaster for the region". House Minority Leader Kevin McCarthy, Senate Majority Leader Mitch McConnell, Senate Minority Leader Chuck Schumer and the chairs and ranking members of House and Senate intelligence and armed services committees are invited.
Tensions were further fuelled on Monday when Iran said its stockpile of low-enriched uranium would next week exceed limits it agreed with worldwide powers in 2015.
All this has raised fears that a miscalculation or further rise in tensions could pull the US and Iran into an open conflict.
Following the attacks on the Norwegian and Japanese oil tankers last week, senior USA military officials said the risk for miscalculation was growing.
Kouhmobarak is some 1,200 kilometres (750 miles) southeast of Tehran and is close to the Strait of Hormuz.
"We give a decisive warning against illegal and aggressive entry of any foreign intruding object and aircraft into the country's sky, and against any violation of the Islamic Republic of Iran's territories", he added.
The Wednesday night downing of the RQ-4 comes days after American officials allege that Iranian forces fired a surface-to-air missile at a U.S. While an American official told CNN that it was a MQ-4C Triton, Iran's Revolutionary Guard claimed it was a RQ-4 Global Hawk.
The Guard described the drone as being launched from the southern Persian Gulf but did not elaborate. AP journalists saw the drones on the base's tarmac during a March 2016 visit by then-Vice President Joe Biden.
The U.S. Navy MQ-4C Triton was shot down by an Iranian surface to air missile while the reconnaissance drone was flying in worldwide airspace over the Strait of Hormuz on Thursday, a U.S. official told ABC News.
"The aircraft was over the Strait of Hormuz and fell into worldwide waters".
"This was an unprovoked attack on a United States surveillance asset in global airspace, " said Captain Bill Urban, CENTCOM spokesman.
Shortly before Trump spoke, at a photo opportunity with visiting Canadian Prime Minister Justin Trudeau, Air Force Lt. Gen. Joseph Guastella, commander of U.S. Central Command air forces in the region, took a different tack from Trump's idea of an accidental shootdown.
He said, "Our air space is our red line and Iran has always responded and will continue to respond strongly to any country that violates our air space". Pompeo made a surprise trip to Baghdad just before it was revealed Iran had loaded missiles into boats and aimed them toward American assets.
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