By Yimou Lee and Thu Thu Aung
NAYPYITAW (Reuters) - Myanmar expects to sign an accord on Thursday over terms for the return of hundreds of thousands of Rohingya Muslims who have fled to Bangladesh, a government official said, amid concern that Myanmar's powerful generals could prove obstructive.
Rights groups have accused the military in mostly Buddhist Myanmar of carrying out mass rape and other atrocities during a counter-insurgency operation launched in late August in retaliation for attacks by Rohingya militants in Rakhine State.
On Wednesday, the United States said the military operation that drove 620,000 Rohingya to seek sanctuary in neighboring, largely Muslim Bangladesh, amounted to "ethnic cleansing", echoing an accusation first leveled by top U.N. officials in the early days of the humanitarian crisis.
In a further warning to Myanmar's military, the U.S. Secretary of State Rex Tillerson raised the threat of targeted sanctions against those responsible for what it called "horrendous atrocities".
For now though, Myanmar is seeking to ease international pressure by striking an initial agreement on returns, while Dhaka wants to ensure overstretched refugee camps that have mushroomed in the Cox's Bazar region don't become permanent.
In addition to the talks on the Rohingya who have fled since Aug. 25, Bangladesh was also likely to raise the plight of hundreds of thousands of Rohingya sheltering in Bangladesh following previous spasms of violence in Myanmar.
A spokesman for Myanmar's Ministry of Home Affairs said discussions with Bangladesh officials on Wednesday had finalised the terms of a memorandum of understanding on repatriation.
"The discussion was finalised yesterday morning, and the MOU will be signed today," Police Colonel Myo Thu Soe said, declining to provide details of the deal.
Myanmar civilian leader Aung San Suu Kyi was set to meet Bangladesh foreign minister Abul Hassan Mahmood Ali on Thursday ahead of the signing.
Suu Kyi, whose reputation as a Nobel peace prize winner has suffered during the crisis, has said repatriation of the largely stateless Muslim minority would be based on residency and that it will be "safe and voluntary".
Her less than two-year-old civilian administration still has to share power with the military who ruled the country for decades, and Myanmar's generals have appeared less enthusiastic about the prospect of Rohingya returning.
Humanitarian workers told Reuters they were particularly concerned about a statement the army commander in chief, Senior General Min Aung Hlaing, made after his meeting with Tillerson last week.
"The situation must be acceptable for both local Rakhine ethnic people and Bengalis, and emphasis must be placed on wish of local Rakhine ethnic people who are real Myanmar citizens," Min Aung Hlaing said in the statement.
His use of the term Bengali for the Rohingya implies they from Bangladesh, and Buddhists in Rakhine are largely opposed to their presence.
Min Aung Hlaing, over whom Suu Kyi has no control, also said the returnees will be "scrutinized and re-accepted under the 1982 Citizenship Law and the 1992 Myanmar-Bangladesh bilateral agreement".
The 1982 law, passed during the junta's long rule, ties Myanmar citizenship to membership of recognized ethnic groups, an official list that excludes the Rohingya.
During a meeting with a senior Chinese general in Beijing on Wednesday, Min Aung Hlaing was told that China wants closer ties with Myanmar's military.
Senior U.N. officials based in Myanmar told Reuters that they feared that security personnel in key positions may not cooperate with the return of Rohingya.
Spokespeople for Myanmar's military were not immediately available for comment.
Diplomats and aid workers have said the key elements of the repatriation deal will be the criteria of return, the participation of the international community, such as the United Nations refugee agency.
Other important points include safeguards for the Rohingya against further violence, a path to resolving their legal status and whether they would be allowed to return to their own homes and farms.
(Additional reporting by Antoni Slodkowski, Shoon Naing and Simon Lewis in YANGON; Editing by Simon Cameron-Moore)