The developer who wants to build the first Whole Foods market in Prince George’s County was given an ultimatum this week: Delay the project, or lose town support.

The Cafritz family, in return, asked the county Planning Board to reschedule Thursday’s meeting to discuss a rezoning request until next month.

The action stalls the ambitious project, which would bring a 120-room hotel, 995 residential units, 168,200 square feet of retail and 22,000 square feet of office space to Riverdale Park.

Representatives for the Cafritz family have scheduled additional meetings with officials in Riverdale Park, College Park and University Park to hammer out an agreement about the design, environmental standards and the mitigation of traffic.

The Planning Board is now expected to discuss the proposal during its meeting Jan. 12. The zoning change is needed to build the development.

Riverdale Park made its demands after weeks of tense meetings resulted in a stalemate with Cafritz family.

“We want a high-quality development, a development with a Whole Foods,” Riverdale Park Mayor Vernon Archer said. “But my job is to make sure those who live here don’t get run over.”

The Cafritz family wants to build on 36 acres of wooded property it owns on Route 1 near East-West Highway between Hyattsville and College Park. The development, which would be built in two phases, would be one of the largest infill projects in Prince George’s.

The property, which was used for workforce housing in the 1940s and ’50, is zoned for single-family houses. It would need to be rezoned to allow the mixed-use development.

Riverdale Park officials said in a letter to the Planning Board that it can support the zoning change under several conditions. Those include: building a crossing, probably a bridge, over the CSX tracks to the east, which would allow for better access to the project; reconfiguring the surface parking lots and landscaping to “create a true gateway into the community”; improving the hiking and biking trails and lanes near the project; and revising the traffic-impact study before any building permits are released.

Many residents and town officials have said the project should be a non-starter without a commitment to construct the CSX crossing.

A representative for the Cafritz family said the delay should not affect the developer’s plans to open the Whole Foods in late 2014. Whole Foods is the anchor in the first phase of the project.

“We remain optimistic,” said Chip Reed, an attorney for the Cafritz family. “A lot of progress has been made, and everybody seems to be trying to work together.”

Reed said the new hearing date should give him enough time to garner support from the town before it goes before the county Planning Board, whose approval is needed for the zoning change. The towns have no zoning authority, but local support will help ensure passage of the zoning proposal.

Joe Kelly, who has lived in Riverdale Park for 26 years, said the developer is trying to “stick a square peg in a round hole” by placing a mixed-use development in the middle of a neighborhood of houses. Kelly said that the county needs more commercial development but that the Riverdale Park site is ill-suited for it.

Officials for County Executive Rushern L. Baker III (D) and several members of the county’s delegation to the Maryland General Assembly have also been working behind the scenes to move the project forward.

Sen. Paul G. Pinsky (D-Prince George’s), who represents the towns and has helped facilitate some meetings between the developer and officials, said he will support whatever the towns decide. But he said he thinks the project would enhance the Route 1 corridor.

“Is it a perfect project? No, it’s not perfect,” Pinsky said. “But I think it will bring some amenities. It could be a positive — if it’s done right.”