The White House on Thursday expressed concern about Iran's alleged role in stoking violence in Yemen, the latest flashpoint in tensions between Middle East powers.
Amid a Saudi-led military offensive to defeat pro-Iran rebels that control much of Yemen, a National Security Council official told AFP that Tehran's actions were destabilising and threatening Yemen's government.
"We have concerns about Iranian activities in Yemen and reports of Iranian flow of arms into Yemen," Alistair Baskey said.
The actions, he added, were "contributing to destabilizing the situation and contributing to the threat posed to the legitimate government."
Huthi Shiite rebels have taken control of several cities and are assaulting the port of Aden, where President Abedrabbo Mansour Hadi had been based before fleeing to Riyadh.
The White House has said there is no evidence that Iran had command and control over the Huthi.
The United States has announced it would provide "logistical and intelligence support" to the Saudi-led military attack.
Officials said that could mean providing refuelling and early-warning radar aircraft support.
About a dozen US military personnel are taking part in a "joint planning cell" at an undisclosed base in Saudi Arabia to coordinate American help to the Gulf states, officials said. And it was likely the team would expand in coming days.
US involvement and its criticism of Iran come at a sensitive time.
Negotiators from six countries -- including the United States -- are currently engaged in talks with Iran, in a bid to scale back its nuclear program.
A senior US official said those talks should not be affected by events in the Gulf.
It has "no impact" said the official, "as we have always been clear that the p5+1 negotiations are solely focused on the nuclear issue."
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