Ambiguity continues to persist over whether the White House would let Yemeni President Ali Abdullah Saleh enter the US for medical treatment.
"What we are looking at now is a request to come to the United States for the sole purpose of medical treatment," Mark Toner, State Department spokesman, said on Tuesday, refusing to go into the specific of the evaluation.
Toner declined to elaborate on the assurances the US wanted from Saleh or offer a timetable for a decision.
"That permission has not been granted yet," he said.
David Mack, former US ambassador to the UAE, told Al Jazeera that "it is really part of our overall relations with Gulf Co-operation Council states, who brokered the deal for Saleh to transfer power in return for some guarantees from criminal and political prosecution".
"Secondly, our ongoing co-operation with current Yemeni transitional government under vice president [Abd-Rabbu Mansour] al-Hadi," he said.
"This ongoing co-operation in the area of counter-terrorism is quite vital to the US position in that struggle."
"Quite frankly, the immunity is essential, he would not agree to leave the country without that immunity that has already been guaranteed by the GCC states in an agreement that we backed," the former US ambassador said.
"So, we are basically implicitly supporting the idea of immunity provided he gets totally out of politics and doesn’t engage in politics while he is in this country," he said.
Even as the Yemeni president awaits his visa, more than 10 people have been killed in the latest exchange between pro-Saleh forces and opposition demonstrators.
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The US regards Saleh as a valuable ally in the battle against al-Qaeda, but it has also condemned his crackdown against pro-democracy protestors in Yemen, which has killed hundreds.
Political asylum for Saleh in the US, or the appearance of preferential treatment from an administration that has championed peaceful and democratic change, would be highly unpopular with Yemenis who have fought to depose their dictator of 33 years.
Saleh was injured in an assassination attempt in June, which forced him to go to Saudi Arabia for treatment.
Last month he signed a deal to hand over powers under an agreement brokered by the Gulf Co-operation Council, which also provided him immunity from prosecution.