By Regan Doherty and Amena Bakr
DOHA/DUBAI (Reuters) - Qatar joined other Gulf Arab states in welcoming Egypt's interim ruler on Thursday in an apparent attempt to salvage diplomatic prestige after the ousting of Cairo's Islamist government which it had backed with billions of dollars in aid.
Qatar has been a regional maverick for its support of Arab Spring revolts and its aid to Muslim Brotherhood rule in Egypt alarmed neighboring Gulf dynasties who see the Islamist group as a potential threat to their own hereditary authority.
Qatar had extended $7.5 billion in loans or grants to Egypt since a revolution toppled veteran President Hosni Mubarak in 2011, providing much of it during the administration of Mohamed Mursi, an Islamist elected in June 2012.
Mursi was overthrown by the army on Wednesday and Adli Mansour, hitherto head of the supreme constitutional court, was sworn in on Thursday as interim president.
Qatar's new emir, Sheikh Tamim bin Hamad Al Thani, "sent a cable of congratulations" to Mansour on the occasion of his taking the oath of office, the official Qatar News Agency said.
The agency quoted a foreign ministry source as praising the Egyptian army's role in safeguarding Egypt's national security, saying Qatar respected the will of the Egyptian people.
The statement made no mention of Mursi or the Brotherhood, a notable omission from a country that has used its energy wealth to pursue what was widely seen as a pro-Islamist foreign policy.
Qatar, which had previously led other Gulf Arab states in welcoming change in the Middle East, was hours behind others this time.
Qatar's allies in the six-member Gulf Cooperation Council, including Saudi Arabia, the United Arab Emirates, Kuwait and Bahrain had earlier sent congratulatory messages to Mansour.
Qatar's outspoken support for rebels fighting to topple Syrian President Bashar al-Assad has alarmed the United States and some Arab allies who fear that weapons supplied by Doha have ended up in the hands of al Qaeda-type militants there.
Qatar had earlier played a central role in supporting the armed revolt that overthrew Libya's Muammar Gaddafi in 2011.
LESS ISLAMIST-FRIENDLY POLICY?
The accession of Sheikh Tamim last week has stirred speculation that he may adopt a less Islamist-friendly policy now that Sheikh Hamad bin Jassim al-Thani is no longer foreign minister. Sheikh Hamad lost his job as prime minister and foreign minister in a cabinet reshuffle after Tamim took power.
Jane Kinninmont, a Gulf expert at Chatham House, a London think tank, said Tamim's June 26 accession speech suggested he might want to mend fences to a degree with fellow Gulf monarchies.
Sheikh Tamim said Qatar was "not affiliated with one trend against the other" - a phrase widely taken to mean the Muslim Brotherhood. Qatar, he said, was committed "to its responsibilities towards Arab cooperation within the framework of the Gulf Cooperation Council and the Arab League".
Kinninmont said Qatar had been under pressure for some time to rebalance its foreign policy priorities. Now, with the Egyptian turmoil, the Qataris "won't want a new administration there (in Egypt) to see them as enemies."
Michael Stephens, researcher at the Royal United Services Institute based in Doha, said Qatar had no choice but to congratulate Mansour. "Qatar is in a position where its ally is gone, and the potential for losing its influence in Egypt has reached a critical level," he said.
"The winds are now blowing in a certain direction, and they've got to make sure they get out of the way. Anything they can do now to reset the switch is a positive move."
(Reporting by Amena Bakr, Mahmoud Habboush and William Maclean, Editing by Sami Aboudi and William Maclean/Mark Heinrich)