US acting Defense Secretary Patrick Shanahan said on Monday he had approved sending a carrier strike group and bombers to the Middle East because of indications of a "credible threat by Iranian regime forces," but did not provide any details on the underlying intelligence, Reuters reports.
US national security adviser John Bolton said on Sunday the United States was deploying the Abraham Lincoln carrier strike group and a bomber task force to the Middle East to send a message to Iran.
While neither Shanahan nor Bolton provided details on US intelligence, other US officials told Reuters there were "multiple, credible threats" against US forces on land, including in Iraq, by Iran and proxy forces and at sea.
"(It) represents a prudent repositioning of assets in response to indications of a credible threat by Iranian regime forces," Shanahan said on Twitter.
Still, questions remain on what specific intelligence- gathering method was used, how relevant the intelligence was, and how those threats differ from the usual concern about Iranian military activity in the region.
"We call on the Iranian regime to cease all provocation. We will hold the Iranian regime accountable for any attack on US forces or our interests," Shanahan added.
In a statement later on Monday, the Pentagon said the step was taken in response to "indications of heightened Iranian readiness to conduct offensive operations against US forces and our interests."
While Iran has not yet responded to the recent moves by the US military, Iranian Foreign Minister Mohammad Javad Zarif told Reuters recently that he did not believe US President Donald Trump wanted war with Iran, but that a "B-team," including Bolton, an Iran hawk, and conservative Israeli Prime Minister Benjamin Netanyahu could goad Trump into a conflict with Tehran.
Three US officials, speaking on condition of anonymity, told Reuters on Monday there were also concerns about US forces in Syria and in the waters nearby in addition to the threats to personnel in Iraq.
One of the officials said the intelligence was specific enough that it detailed the locations of potential attacks against US forces and the time frame within which they could occur. The official added that the threat was not only against US forces in Iraq but those coming in and out of the region.
The Abraham Lincoln carrier strike group, which was ordered to the Middle East, was expected to go to the region eventually, but its movement was "expedited" because of the threat, another US official said.
The official said it would still take at least several days for the carrier strike group to reach the Middle East because it would have to slow down to go through the Suez Canal and the hope was that the announcement on Sunday would act as a deterrent itself.
The Trump administration's efforts to impose political and economic isolation on Tehran began last year when it unilaterally withdrew from the nuclear deal it and other world powers negotiated with Iran in 2015.
US Secretary of State Mike Pompeo, speaking in Finland where he was attending the Arctic Council meeting, said on Monday the United States has seen activity from Iran that indicated a possible "escalation."
In September, the United States said it would effectively close its consulate in the Iraqi city of Basra, following increasing threats from Iran and Iran-backed militia.
There are currently about 5,200 US troops in Iraq and under 2,000 American forces in Syria.
The action marked the latest in a series of moves by Trump's administration aimed at ratcheting up pressure on Iran. Some experts have raised a concern about Bolton's focus on Iran and point to his history of being at odds with US intelligence community assessments on Iran.
In a 2017 article in the conservative National Review magazine, Bolton charged that Iran committed "significant violations" of the 2015 nuclear accord.
Yet, US intelligence agencies have consistently assessed Iran to be in compliance with the deal and that the agreement to prevent Iran from developing a nuclear warhead was working as designed.
Some have said the United States must be careful not to end up with a situation like 2003, when prior to the invasion in Iraq, President George W. Bush and top aides made the case for intervening by citing intelligence that Iraqi President Saddam Hussein had ties to al Qaeda and was secretly developing nuclear, chemical and biological weapons.
Both claims were proved false.