(Adds U.S. meetings in Myanmar, paragraphs 4-5)
By Praveen Menon and Amy Sawitta Lefevre
KUALA LUMPUR/BANGKOK May 21 (Reuters) - Malaysia's Prime Minister Najib Razak said on Thursday he had ordered the navy to rescue thousands of migrants adrift at sea, and a Thai official said Myanmar had agreed to attend an emergency conference on the crisis.
Diplomats say Myanmar had up to now resisted calls for it to take part in meetings on the stranded "boat people," many of them Rohingya Muslims who have long complained of discrimination in Myanmar.
The apparent shift in its position came after Malaysia and Indonesia's foreign ministers held talks with senior officials in Myanmar on Thursday. Western powers and aid groups have also urged Myanmar to increase its involvement, and called on regional powers to do more.
U.S. Deputy Secretary of State Antony Blinken also held meetings in Myanmar on Thursday, seeing its president, foreign minister, parliamentary speaker and military commander.
Blinken stressed the need for Myanmar to address the root causes of the migration, "including the racially and religiously motivated discrimination and violence," State Department spokeswoman Marie Harf told a news briefing.
The crisis has seen thousands of migrants, also including Bangladeshis fleeing persecution and poverty at home, pushed back out to sea by Thailand, Malaysia and Indonesia.
Many now face sickness, and possible starvation, say aid groups.
"I have further ordered @tldm_rasmi (navy) and APMM (Malaysian Maritime Enforcement Agency) to conduct search and rescue efforts on Rohingya boats," Najib said on his Twitter account.
"We have to prevent loss of life," he said, adding that humanitarian aid would be delivered by land and sea.
Malaysia and Indonesia on Wednesday said they would let as many as 7,000 migrants on the seas now to come ashore temporarily, but no more.
A Thai official told Reuters Myanmar had agreed to attend a regional summit on the issue in Bangkok next week, without going into further details. Officials in Myanmar did not respond to requests for comment.
Rohingya Muslims have complained of state-sanctioned discrimination in majority-Buddhist Myanmar and are denied citizenship. Myanmar denies discriminating against the group and has said it is not the source of the problem.
Indonesia and Malaysia have said that temporary shelters would be set up to house the migrants but Thailand, a traditional transit point for migrants trying to reach Malaysia illegally to find work, said it would not follow suit.
"There will definitely be no migrant shelters," Thai Prime Minister Prayuth Chan-ocha told parliament in Bangkok on Wednesday, adding that existing detention centers would be used to hold those found to have entered Thailand illegally.
Thailand has said it will stop towing boats back to sea, something Malaysia and Indonesia had been doing in recent days. It has also said it will allow the sick to come to shore for attention, but has stopped short of saying whether it will allow other migrants to disembark. (Additional reporting by Kaweewit Kaewjinda in BANGKOK, Kanupriya Kapoor in JAKARTA and David Brunnstrom in WASHINGTON; Editing by Nick Macfie)