By Wa Lone

(Reuters) - Three ethnic armed groups excluded from Myanmar's peace process will no longer be required to surrender, prior to joining the talks, a Myanmar military negotiator said on Thursday, a softening of the armed forces' tone toward the insurgents.

Fighting on the eastern border with China last year pitted the military against the predominantly ethnic Chinese Myanmar National Democratic Alliance Army (MNDAA), and its allies, the Ta'ang National Liberation Army (TNLA) and the Arakan Army (AA).

Until now, the military has demanded that the three groups disarm before being allowed to join peace negotiations that include other Myanmar ethnic armed organizations.

But the army has relaxed that demand after the groups have shown "they really wanted peace", Khin Zaw Oo, a member of the Myanmar Peace Commission, told Reuters in an interview.

"Previously, we made the exact demand that they lay down their arms if they wanted to get involved in the peace process - they have found that difficult to accept," said the retired lieutenant general, who is due to meet the armed groups soon.

Instead, he added, the army now wants the rebels to issue a statement "showing their political willingness to abandon their weapons".

Khin Zaw Oo declined to say exactly what this would entail, however.

"It does not mean surrender, they just have to show their desire and willingness," he said. "Because we want all of them to be included. That's why we relaxed that previous condition. We agreed to solve their difficulty to comply with our demand."

Khin Zaw Oo and two members of the peace panel will meet the groups "very soon" to discuss conditions for their participation in a nation-wide peace conference planned for the end of August.

The decision to meet the groups and potentially invite them to join nationwide ceasefire negotiations is a departure in the stance of the armed forces, which have so far flatly refused to recognize them as legitimate parties in talks.

The army and government leader Aung San Suu Kyi share the same goal of ending the armed conflict before the next elections in 2020, Khin Zaw Oo said.

"We are working toward democracy," he added. "That's why we want to see all armed groups enter politics together, with no armed conflict."

(Reporting by Wa Lone; Editing by Clarence Fernandez)