Maryland lawmakers will not pass the centerpiece of Gov. Martin O’Malley’s environmental agenda, a plan to build one of the nation’s first offshore wind farms in the Atlantic Ocean, before they adjourn Monday, according to multiple sources close to the negotiations.

 Sources in both chambers of the state’s General Assembly say lawmakers are expected to agree to further study the estimated $1.5 billion project in coming months and reconsider the legislation either this fall when they reconvene in a special session for redistricting, or in their 2012 session in January.

O’Malley lobbied lawmakers heavily in recent weeks to pass the measure. It is backed by a coalition of environmentalists as well as unions who believe construction of the massive turbines would bring 2,000 jobs or more to the state, as well as make Maryland a leader in green energy.

But the plan ran into significant opposition from both Republicans and Democrats in the legislature, who said they had too many unanswered questions about the potential costs on the state’s electric ratepayers.

Under a complicated set of steps laid out in the bill, the state would require Maryland utilities to sign 25-year agreements to buy offshore wind power at a price far above the current market rate. The subsidy would go to developers of the offshore wind farm who say they could not secure financing for the project otherwise. The cost would be spread among all residential and commercial customers through a monthly fee on electric bills.

For most residential customers the cost was estimated between $1.44 to $3.61 a month, for large companies and municipalities the surcharge could add up to 2 percent of their bills, or tens of thousands of dollars monthly.

Proponents attempted to counter concerns over the costs, arguing that with similar investments underway in Massachussets, Rhode Island and New Jersey, competition will increase and make the price of wind power competitive with that from fossil fuels. Maryland would also benefit, they said, by locking in a share of its energy prices with wind power for decades.

The House Economic Matters Committee is scheduled to vote on the bill this afternoon. Several lawmakers have prepared amendments to attempt to pass the bill to the House floor, but sources said that was unlikely.