By Tim Hepher and Anshuman Daga
KUALA LUMPUR, March 16 (Reuters) - Malaysia has appealed for help and international coordination in a search for its missing passenger jet that stretches across two corridors from the Caspian Sea to the southern Indian Ocean, diplomats said on Sunday.
Malaysian officials briefed envoys from 22 countries on the progress of the investigation after calling off a search in the South China Sea for the jet that vanished from radar screens more than a week ago, with 239 people on board.
Although countries have been coordinating individually, the broad formal request at a meeting of ambassadors marked a new diplomatic phase in a search operation thought increasingly likely to rely on the sharing of sensitive material such as military radar data.
"The meeting was for us to know exactly what is happening and what sort of help they need. It is more for them to tell us, 'please put in all your resources'," T.S. Tirumurti, India's high commissioner to Malaysia, told Reuters.
The diplomatic initiative could become significant as nations ponder whether to share any military data on the Boeing 777's fate, and fills a void left by the failure of Southeast Asian nations to work as a bloc on the crisis, a diplomat said.
"There are clearly limits to military data," the diplomat said, adding that nations were nonetheless aware of the strong public interest in cooperation on a civilian issue.
Malaysian Defence Minister and Acting Transport Minister Hishammuddin Hussein said Malaysia had itself fed the findings of its own military radar tracks into what is now a domestic criminal enquiry into suspected hijacking or sabotage.
He declined to say whether Kuala Lumpur had asked others to open up their military radar tracks, but told a news conference that it had asked for both primary and secondary radar data.
Experts say military forces mainly use primary or classic radar, which works by listening for its own echo bouncing back off a potentially unfriendly object.
Civil air traffic control mostly uses secondary radar, which relies on hearing a signal sent back from the aircraft's transponder along with data designed to identify the plane.
It was the apparently deliberate decision to turn the jet's transponder off that left Malaysian authorities relying on the blips picked up by primary military radar to form the theory that the aircraft - on a flight to Beijing - had turned back west before disappearing.
Underscoring the caution surrounding the request for deeper co-operation, at least one country represented at Sunday's ambassadorial meeting asked Malaysia to supply its request in writing, a diplomat present at the talks said.
Southeast Asia has been at the centre of a regional arms race for several years amid tensions in the South China Sea, with maritime surveillance and air defences high on the list of hardware laid out at last month's Singapore Airshow.
The search for the missing jet is focusing on a wide stripe of territory either side of two arcs formed by satellite plots of the aircraft's last known possible position.
The northernmost of these stretches runs north through Thailand and China and bends towards India, Pakistan and then Central Asia, over some of the world's most strongly guarded defences.
If the jet did stray into those areas, sensitivities over whether and how such sensitive data could be shared could be further complicated by potential embarrassment over how such a large unidentified aircraft could have continued unchallenged.
Defense analysts said on Saturday that the jet's disappearance raised awkward questions about the strength of regional or even global air defences.
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