YANGON (REUTERS) - Myanmar's military turned down a dinner invitation from opposition leader Aung San Suu Kyi, lawmakers said on Thursday, after the Nobel laureate sought a meeting to build ties ahead of a proposed summit on changing the constitution.

Suu Kyi is barred from becoming president under the existing constitution, which cannot be changed without the support of at least one military lawmaker.

The military holds 25 per cent of the seats in parliament, an effective veto over constitutional amendments which need more than 75 per cent support from lawmakers.

Myanmar emerged in 2011 from 49 years of rule by military generals.

But the initial pace of reform has slowed, prompting international concern that the military is not ready to submit to the authority of the leader of a parliamentary democracy.

The military block sent a letter to Suu Kyi to apologise for being unable to make the dinner in the capital of Naypyidaw due to a prior engagement, said Nyan Win, a spokesman for Suu Kyi's National League for Democracy Party (NLD).

The invite was received at short notice for military lawmakers to change a scheduled meeting, one military parliamentarian told Reuters.

The meeting would have been the first between Suu Kyi and military parliamentarians.

Public debate on the constitution has come to the fore around the visit of President Barack Obama to Myanmar earlier this month.

Obama said it made little sense for the constitution to bar Suu Kyi from becoming president.

The speaker of parliament, Shwe Mann, said last week that the constitution could not be changed before a general election in 2015.

On Tuesday, parliament unanimously endorsed talks among Suu Kyi, President Thein Sein, the speakers of the two houses of parliament, military chief Min Aung Hlaing, and a member of a party representing an ethnic minority.

Suu Kyi has endorsed reforms by the semi-civilian government of former general Thein Sein.

She was famously pictured watching a military parade in Naypyidaw last year, alongside members of the previous junta that had kept her under house arrest for more than 15 years.

But over the past year Suu Kyi has been critical of the government, accusing it of stalling the reform process.

Her party has gathered about five million signatures in support of a petition to amend the military-drafted constitution.

No date has been set for the proposed constitutional talks.