And on Wednesday, the State Department announced it was evacuating all non-emergency staff from neighboring Iraq, closing the USA embassy in Baghdad and the US consulate in Erbil.
That "high level of alert" affects how US troops operate, limiting the movement of non-essential service members and requiring them to bring full equipment "everywhere they go for protection and security", a USA official said on Wednesday.
"U.S. sanctions on Iran are biting, and biting in a very effective way", Gargash said. "The United States Congress must do everything it can to prevent the Trump administration's attempts to put us on the brink of a catastrophic and unconstitutional war with Iran that could lead to even more deaths than the Iraq War". It was unclear how many staff would leave.
Washington has sent additional military forces to the Middle East, including an aircraft carrier, B-52 bombers and Patriot missiles in a show of force against what United States officials have said is a threat to its troops and interests in the region.
Earlier this year, Congress forced Trump into the first veto of his administration over a resolution that passed the House and Senate to halt US involvement in the Saudi-led war against Iranian-backed Houthi rebels in Yemen. A fire also caused minor damage to one pumping station, it said, adding that Saudi Aramco's oil and gas supplies were not affected.
"The U.S. government has limited ability to provide emergency services to U.S. citizens in Iraq".
Paramilitary groups trained, armed and advised by Iran have played an important role in the battle against IS in Iraq.
Iran denied involvement, though it has repeatedly threatened to block the strait, through which streams about a fifth of world's oil shipments, if the United States tries to stop Iran from exporting oil.
Mr Trump's administration has pursued a policy of "maximum pressure" against Iran, including tightening economic sanctions, since withdrawing the United States from a deal created to limit Iran's nuclear program a year ago.
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"I would urge the State Department and DOD to come down here and explain to us what's going on because I have no idea what the threat stream is beyond what I read in the paper", said Sen.
The analyst asked why Iran allows those two countries to run their economic affairs and trade in a normal fashion while Iran is suffering from the impact of sanctions.
Iran's supreme leader issued a veiled threat in the same speech in which he stated that "no one is seeking war", saying it wouldn't be hard for the Islamic Republic to enrich uranium to weapons-grade levels amid rising tensions with the USA, state media reported Wednesday.
The IRGC is directly controlled by the Islamic regime's Supreme Leader Ali Khamenei and Salami was named its head last month.
It has given the European Union, Britain, France, Germany, Russia and China, and Russia, the remaining signatories of the deal, 60 days to come up with a way for it to continue to sell oil and receive the revenues.
Under the deal, Tehran was allowed to produce low-enriched uranium within about a 660-pound limit, and produce heavy water with a stock capped at around 130 tons.
Mr Pompeo told Iraq's top brass to keep the militias, which are expanding their power in Iraq and now form part of its security apparatus, in check, the sources said.
Nevertheless, Iran has relaxed restrictions on its nuclear programme and threatened action that could breach the nuclear deal, although the initial moves do not appear to violate the agreement. "Numerous terrorist and insurgent groups are active in Iraq and regularly attack both Iraqi security forces and civilians".
Iraqi officials have questioned the threat described by the Americans, however, the New York Times reported on Wednesday.