`Contra' leaders seek unity and democratic reform. Nicaraguan rebels are meeting to iron out differences before key aid vote in Congress. But `contra' leader Ed'en Pastora's struggle with Nicaragua is over.

Nicaraguan rebel leaders are expected to start their second week of struggle today to unify and reform their movement. A show of unity of the United Nicaraguan Opposition (UNO) -- the main United States-financed ``contra'' group -- is considered essential to win support in the US Congress for military aid. The contras are fighting to overthrow the Nicaraguan government.

The meeting here of UNO's three-member leadership is expected to end Wednesday. Congress is set to reconsider the controversial aid package June 9.

One source close to UNO was optimistic about the fact that the meetings had held up this long -- an unprecedented length of time for the group to meet, he said. The meetings opened May 12.

Meanwhile, the Contadora group of nations met in Panama in a continued effort to get the Sandinista government in Nicaragua to agree to sign a draft peace treaty for the region. All other Central American member countries have agreed to sign it.

The Contadora group, which is trying to arrange a peaceful settlement in Central America, has set a June 6 deadline for signing the draft. There is general skepticism that Nicaragua will sign by then. Should Nicaragua refuse to sign by June 6, congressional sources say the resultant lack of a treaty will be a strong argument in favor of US aid to the contras.

Although there is division in the Reagan administration and among other US supporters of the contra movement about the role of Contadora, Sen. Richard Lugar (R) of Indiana has suggested that diplomacy -- the Contadora route -- cannot be successful without contra aid. Senator Lugar is the chairman of the Senate Foreign Relations Committee. If the Contadora treaty were signed by Nicaragua, says an aide to Lugar, verification of that nation's compliance might mean withdrawal of US military aid to the contras, but not necessarily the withdrawal of humanitarian aid.

``We have to help build the contras as a legitimate, responsible, and effective political front,'' says the Lugar aide. That front is what the Reagan administration hopes will unify all anti-Sandinista factions into a single military force and diplomatic voice.

That's what the Miami meeting is about. The Reagan administration is pressuring the UNO members to forge convincing reforms that would make UNO more democratic, with decisions made by majority rule and with its army answering to the full leadership rather than to a single strong man, as it now does.

The majority-rule issue is the most crucial of three issues on the agenda, says a rebel source. So far, besides finishing with one unspecified agenda item, the leaders have taken time to meet with US special envoy Phillip Habib, whom they called to Miami to ``discuss where the contras stand with the Reagan administration,'' says the source.

Though this source would not discuss what the agenda items are specifically, he did say that broadening the directorate of UNO is not being considered now, but may be in the future.

This is the first time UNO has attempted to build a firm institutional framework from which to work, a rebel source says. But the group is reported to have been bitterly struggling and close to breaking up at times this past week.

The division of the three UNO leaders -- who were locked in secret meetings here over the weekend -- has been Alfonso Robelo Callejas and Arturo Cruz, former Sandinista supporters, on one side and Adolfo Calero, a conservative, on the other. By virtue of heading the largest guerrilla military force, the Nicaraguan Democratic Force (FDN), Mr. Calero has been considered the UNO strong man.

Mr. Cruz and Mr. Robelo have sought more control over the military wing of UNO as well as ``democratic reform'' in the decisionmaking structure of the group, such as majority rule.

Cruz and Robelo's position has been strengthened. Rep. Dave McCurdy (D) of Oklahoma, the leader of the 30-member group whose swing vote is needed to win contra aid, says an aid package will not pass without Cruz remaining as a leader of a reformed UNO. The Reagan administration's push for an UNO pact has been a tacit point in favor of Cruz and Robelo.

``Cruz and Robelo have a lot of momentum. . . . They've got the swing vote from Congress, they've got the State Department [behind them], they've got military punch now, and the vast majority of people in the opposition are behind them,'' says Robert Leiken, a Central American scholar with the Carnegie Endowment for International Peace.