ROCKLAND, Maine — The city is awaiting a letter from the company that wants to build a $200 million natural gas plant before the next steps on negotiations start.

City Manager James Chaousis met Tuesday with representatives of Rockland Energy Center, the subsidiary of Boston-based Energy Management Inc., which has proposed buying for its project 18 city-owned acres that encompass the land where City Hall and public services are located.

Last week the City Council reversed an earlier vote and unanimously agreed to grant a nonbinding option on the properties to Rockland Energy Center. Chaousis said this week the company will be submitting a letter to the city in which it will offer more details on its proposal.

The manager said that letter will determine the next steps the city must take as it begins negotiations.

Chaousis said a lot of work needs to be done. That work includes the city doing its due diligence to determine whether the City Hall site is the best location for the plant and whether there could be a better location in Rockland. The city also must determine what the best use for the city properties are and where to relocate City Hall and public services should the deal go through.

The council vote Friday came on the same day as the deadline for companies to submit contract bids to the Public Utilities Commission for providing electricity on a long-term basis. Rockland Energy representative Evan Coleman said the option on the Rockland properties was needed before the company were to submit its bid.

Harry Lanphear, administrative director of the PUC, said Monday a bidder did not need an option, but it did need to have a “sufficient level of site control” that would be acceptable to ISO New England, the organization that oversees the New England power grid. ISO stated a potential energy provider either must own, lease, have an option to buy or have an easement on the property.

The PUC official said he could not reveal whether Rockland Energy submitted a bid nor how many bids were received. He said information is confidential by law. Coleman did not return a telephone request for further comment left Monday.

There is no set time for when the PUC will make a decision, Lanphear said. The staff must review each bid, and generally a lot of questions are asked to clarify points in submitted proposals. The staff will then make a recommendation to the PUC commissioners who will vote on whether to accept proposals that will allow a bidder or bidders to negotiate long-term contracts with Central Maine Power and Emera Maine for its electricity consumers.

Rockland Energy Center’s option on the Rockland property is nonbinding, and no sale could occur before Aug. 31 under the agreement. A final sale would need to be approved by voters at a referendum.

Coleman said last week the natural gas plant would provide significant tax revenues to the city, scores of construction jobs, 12 to 18 permanent jobs that will pay more than $60,000 annually and low-cost steam that could lower operating costs for other local industries. The cogeneration facility would generate electricity and steam.

Opponents who spoke out last week criticized the speed at which the council voted and voiced concern over the environmental impact of a natural gas plant.