The United States has said that it was very concerned by video of a member of the ruling family of Abu Dhabi allegedly torturing an Afghan man, footage that could stall a civilian nuclear deal with the United Arab Emirates.

State Department spokesman Ian Kelly said the department was consulting with Congress about the agreement, which could be blocked if an outcry over the video grows. The deal could be worth billions of dollars to US energy companies that build and operate nuclear power plants.

'We, of course, are very concerned by this video,' Kelly told reporters when asked whether the 2004 torture video was holding up implementation of the agreement, which was signed in the final days of the former Bush administration and has to be sent to Congress for review by President Barack Obama.

'We think it's an important agreement, but, as I said, we are right now in the stage of having consultations with Congress,' Kelly said. 'At the appropriate time, we'll make the decision,' he told reporters.

In part of the video, which has been shown on US television networks as well as at a congressional hearing on Wednesday, an Afghan man is shown being abused with an electric cattle prod, beaten with whips and a plank of wood with a nail on it and driven over by a car at a desert location in 2004.

Kelly declined to draw a link between the video and possible stalling on the deal. But another US official, who declined to be named, confirmed the graphic footage was an issue.

Some lawmakers also believe the UAE is not doing enough to curb Iran's atomic ambitions. They also want more transparency over the nuclear deal that establishes a legal framework for commerce in nuclear energy between the United States and UAE.

A senior US official, who spoke on condition of anonymity as the issue is sensitive, said the video was 'shocking' and that the Obama administration had discussed it with the UAE.

'We have urged them to have a thorough and prompt review and to take appropriate follow-up action,' said the official.

The senior official refused to speculate on when Obama might sign off on it. 'I will not comment on internal deliberations or speculate about timing,' the official said.

Abu Dhabi's judicial department said on Monday that prosecutors had detained Sheikh Issa bin Zayed Al-Nahyan, a brother of the UAE crown prince, pending an outcome of an investigation into the video. -Reuters