Myanmar's ruling party was set on Tuesday to propose changes to the constitution, a member of parliament and a party source said, its biggest challenge in nearly three years to the military's power over politics as enshrined in the charter.

The proposal could add to tension between the military and Aung San Suu Kyi's National League for Democracy (NLD), which have been at loggerheads over the charter since the party's historic landslide election win in 2015.

‘Election promise’

The surprise bid to reform the constitution comes as both civilian and military leaders face growing international pressure over an army crackdown on Rohingya Muslims in 2017 that sent about 7,30,000 people fleeing to neighbouring Bangladesh.

“They are going to submit the proposal today,” Ye Htut, an NLD member of the upper house, for the northern region of Sagaing, told Reuters . “It is the election promise.”

The 2008 charter, drafted during military rule, guarantees the army a quarter of seats in the two houses of the Parliament. Constitutional changes require votes of more than 75 percent, giving the army an effective veto.

The constitution also blocks Suu Kyi from becoming President as it contains a prohibition on presidential candidates with foreign spouses or children. Suu Kyi had two sons with her late British academic husband.

For nearly three years, she has ruled from “above the president” by creating a new position of State Counsellor.

The constitution also gives military control of key security ministries, including Defence and Home Affairs.

Full transition to democracy

Nobel Peace laureate Suu Kyi has long spoken of her aim to reform the constitution as part of a democratic transition after 50 years of strict military rule. “The amendment of the constitution was one of the goals of our government,” she said during a forum in Singapore in August. “The completion of our democratic transition must necessarily involve the completion of a truly democratic constitution.”

But the military has for decades seen itself as the only institution capable of preventing the disintegration of the ethnically diverse country, and has stressed the importance of its constitutional oversight of the political system.

An adviser to Suu Kyi who openly called for reforms to reduce the military’s role, Ko Ni, was shot dead in broad daylight at the Yangon International Airport exactly two years ago, on January 29, 2017. While no evidence has emerged that his call for constitutional reform led directly to his murder, or that active military officials ordered the killing, his death cast a pall over reform efforts.

It was not clear what provisions of the constitution the NLD's proposal would target or whether the party had secured the buy-in from the military necessary to pass any such measure.

In the past, some members of Suu Kyi's party have expressed their desire to amend Article 436, which gives the military the effective veto over constitutional reform. At a short meeting with its MPs on Monday, the party's central executive panel briefed them on the plans for Tuesday's vote, said Ye Htut, who attended the gathering.

A second party source confirmed the amendment motion was to be presented on Tuesday.

Party spokesman Myo Nyunt declined to comment. Reuters was unable to seek comment from the parliamentary office. The parliamentary agenda reviewed by Reuters does not show the proposal, but political analyst Yan Myo Thein said it was possible to submit a new one at the end of the session, with the speaker's approval, or call an afternoon session to submit it.