Under a starry sky, US Navy fighter jets catapulted off the aircraft carrier's deck and flew north over the darkened waters of the northern Arabian Sea, a signal to Iran that the foremost symbol of the American military's global reach is back in its neighbourhood, perhaps to stay.

The USS Abraham Lincoln, with its contingent of Navy destroyers and cruisers and a fighting force of about 70 aircraft, is the centerpiece of the Pentagon's response to what it calls Iranian threats to attack US forces or commercial shipping in the Gulf region. In recent years, there has been no regular US aircraft carrier presence in the Middle East.

US officials have claimed that signs of heightened Iranian preparations to strike US and other targets in the waters off Iran as well as in Iraq and Yemen in late April emerged shortly after the Trump Administration announced it was clamping down on Iran's economy by ending waivers to sanctions on buyers of Iranian crude oil. The Administration went a step beyond that at the weekend, announcing penalties that target Iran's largest petrochemical company.

Yesterday the Lincoln was steaming in international waters east of Oman and about 320km from Iran's southern coastline. One month after its arrival in the region, the Lincoln has not entered the Gulf, and it's not apparent that it will. The USS Gonzalez, a destroyer that is part of the Lincoln strike group, is operating in the Gulf.

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Rear Admiral John Wade, commander of the Lincoln strike group, said Iran's naval forces have adhered to international standards with ships in his group. "Since we've been operating in the region, we've had several interactions with Iranians. To this point all have been safe and professional — meaning, the Iranians have done nothing to impede our manoeuverability or acted in a way which required us to take defensive measures."

The Lincoln's contingent of 44 Navy F-18 Super Hornets are flying missions off the carrier night and day, mainly to establish a visible US "presence".

Marine General Frank McKenzie, the head of Central Command, said he thinks Iran had been planning some sort of attack on shipping or US forces in Iraq. Two other officials said Iran was at a high state of readiness in early May with its ships, submarines, surface-to-air missiles and drone aircraft.

"They are looking hard at the carrier because they know we are looking hard at them," McKenzie said.

Iran's economy is being squeezed hard by US sanctions. Iran's Revolutionary Guard has said it doesn't fear a possible war with the US.

- AP