Myanmar set up a committee to discuss reforming the country's military-drafted constitution on Tuesday, pitting Aung San Suu Kyi's civilian government openly against the powerful armed forces for the first time over the incendiary issue.
Suu Kyi's National League for Democracy (NLD) party won a landslide in 2015 elections, but was forced into an uneasy power-sharing agreement with the armed forces.
Under a 2008 charter it drafted, the military controls all security ministries and is gifted a quarter of parliamentary seats.
That hands the army an effective veto over any constitutional change.
Suu Kyi's party has promised to reform the controversial document.
With 2020 polls looming, parliament voted overwhelmingly Tuesday to form a cross-party committee to debate reforms of the charter.
The main purpose of the "all-inclusive" panel will be to "write a bill to change the 2008 constitution", deputy speaker and committee chair Tun Tun Hein, an NLD lawmaker, told parliament.
The NLD will be allocated 18 out of 45 seats on the panel, the military will have eight and the remainder will be divided between other parties.
There has so far been no detail about the specific reforms the discussions would focus on, or the steps ahead once the panel makes its recommendations.
But its formation threatens a political showdown with the army, whose bloc of MPs stood up in protest early February when the committee's formation was first mooted.
However, the army chief struck a more conciliatory tone in a rare interview with foreign media last week.
"We accept that the constitution needs amendments," he told Japanese paper Asahi Shimbun.
"But the important point is that no amendment should harm (its) essence."
The move by parliament came just a few days after a court handed death sentences to the killers behind the 2017 murder of Muslim lawyer and Suu Kyi advisor Ko Ni.
He was leading the charge on constitutional reform when he was shot dead in cold blood, while cradling his grandson.
Ko Ni is also credited with Suu Kyi's circumnavigation of a clause banning anyone married to a foreigner from becoming president.
Suu Kyi, whose late husband was British academic Michael Aris, created her current post of state counsellor above the president's office.
Forming the cross-party committee is "very significant", analyst Khin Zaw Win, director of Yangon-based Tampadipa Institute, told AFP, adding there could be a "reckoning of sorts" approaching between the NLD and army.
"It will need a lot of ingenuity and creativity from everyone."