Sutton Place has opened a second front in its tussle with a developer over a nearly 800-foot-high co-op slated for East 58th Street.

City planning officials were quick to raise concerns this summer with a proposal put forward by the East River 50s Alliance, a neighborhood group, that would have capped new, residential towers in the area at 260 feet.

After months of talking with city planners, the group withdrew its proposal this week and submitted a second plan that, according to the developer, Gamma Real Estate, could still threaten the tower.

“You might call this a compromise,” said Alan Kersh, head of the East River 50s Alliance, which believes the condos will tower over Sutton Place and change the area’s character. “We read the tea leaves, and we saw the resistance.”

The alliance has ditched height limits in favor of pushing for tower-on-a-base standards in the area east of First Avenue between East 51st and 59th streets.

If passed, the rules would ensure that new, taller buildings concentrate 45 to 50 percent of their bulk below an altitude of 150 feet. The remaining 50 to 55 percent of the building could rise in a tower above this wider, base.

City planners believe focusing on the tower-on-a-base model will ensure that new buildings better compliment the area’s architecture, according to a Planning Department spokesman.

The alliance’s plan could halve how tall Gamma is permitted to build at 438 E. 58th St., where it is currently working on the foundation for the controversial co-op.

If the city approves the alliance’s plans and Gamma’s project is not grandfathered in under the old rules, constructing a co-op that abides by the new standards would not be financially feasible, according to Gamma’s president Jonathan Kalikow.

“The precedent it will set will mean that even if you buy something with an as-of-right zoning [project in mind], it doesn’t mean anything,” Kalikow said. “That will absolutely hurt pricing for land.”

The alliance’s plan would impact three other sites, where current zoning rules could allow for skyscrapers, according to Kersh.

But Kalikow argued the alliance is targeting his project.

“We are the only site,” Kailkow said, noting that building towers on the other sites would require negotiating with co-ops for additional development rights. “If you have a co-op with 50-plus units, you’re not getting everybody to agree to everything.”

A Planning Department spokesman said city officials were viewing the matter as an application impacting a 10-block area, not a specific site.

The Planning Commission is slated to hold a public hearing on the proposal Oct. 18. After that, Kersh hopes the commission will vote Nov. 1 and send the matter to the City Council for approval before Thanksgiving.

The local community board and borough president opted not to review the new plan, which has expedited the approval process.

Gamma will not be able to finish the foundation by Thanksgiving, which Kalikow said is the only reliable way to ensure the project gets grandfathered in under the old zoning rules.

“It means that we would have to show that we’ve met the criteria for grandfathering, and some of that criteria is less objective,” Kalikow said. “We don’t know how that will play out.”