PORTLAND, Maine — Opponents of Midtown, the much-debated housing and retail complex developers hope to build in the Bayside neighborhood, are gathering this week to strategize.

Meanwhile, the developers are preparing to break ground on the first phase of Midtown as soon as March.

On Jan. 14, the Planning Board approved the first phase of the $150 million development, which would bring four 15-story towers and two parking garages to 3.25 acres of city-owned land along Somerset Street when it’s ultimately completed.

A decrepit area that was formerly home to scrap yards, the land would be sold to The Federated Cos., a Miami-based developer. Federated’s plans for the site include more than 650 market-rate apartments, parking for about 1,100 vehicles, and 100,000 square feet of retail space.

The first phase of the 10-year project, to be built east of Chestnut Street, would include a tower with 235 apartments, 43,000 square feet of first-floor retail space and a 700-car garage.

Plans for Midtown were unveiled in September 2012. But in recent months the project has become a lightning rod for public opinion.

Opponents have said the complex is too large, out of scale with the rest of the city, and inconsistent with the 2000 master plan for Bayside. Supporters claim Midtown would be a boon for the neighborhood and the city, bringing much-needed housing, parking and jobs to a blighted swath of Portland.

Keep Portland Livable, a group of residents leading the opposition, has threatened to appeal the Planning Board decision in court. The deadline for an appeal is Feb. 13.

Peter Monro, co-founder of Keep Portland Livable, on Sunday said the group would be meeting with legal counsel this week to determine if there are grounds for an appeal. But he denied that legal action was simply a tactic to stall the project and ultimately to kill it, as some supporters of Midtown have alleged.

“We would never do that,” he said, claiming the group would appeal “only if we thought we had a legal reason for winning.”

As an alternative, he said Keep Portland Livable might launch a citizen’s referendum to put the project on hold. The group’s goal is not to stop the development, he added, but to scale it down.

Keep Portland Livable also wants to “educate and engage” residents about future development in the city, according to Monro. He said he plans to discuss such goals in an informal public meeting Thursday evening.

But Greg Shinberg, lead consultant on the Federated development team, believes Keep Portland Livable is bent on stopping Midtown — and that those efforts are misguided.

“Stalling this project is not going to kill it, and it would be tragic to try,” he said in an interview. “This is a great project … and I am very confident it can withstand a legal challenge.”

Shinberg said that despite the public opposition to Midtown, he believes “the momentum has turned, and we now have a very strong showing of public support.”

It’s too early to tell how long a potential appeal would delay the project. In addition, building permits must still be obtained, a process that can take several weeks, and the sale of the land is contingent on the permitting. Nevertheless, Shinberg is optimistic that work on Midtown’s first phase could begin in two months and be complete by early 2016.

“I would anticipate in March we’ll have shovels in the ground,” he said. “We’re going full speed ahead.”