BATH — The U.S. Navy on Tuesday came a step closer to exercising its option to build another DDG 51 at Bath Iron Works after the Senate Defense Appropriations Subcommittee included a $100 million “down payment” on the ship in its defense budget bill.

U.S. Sen. Susan Collins, R-Maine, a senior member of subcommittee, said Tuesday that before adjourning, the panel filled part of the funding shortfall of $304 million, and she said “the [sub]committee has essentially committed” to finding the rest of the money.

Although full funding for 10 DDG 51 destroyers over the next five years was appropriated in fiscal year 2013, the across-the-board federal spending cuts known as sequestration led the the Navy on June 3 to award contracts for only 9 ships, with an option for a 10th destroyer. BIW secured contracts for four destroyers, with the option for a fifth, while BIW competitor Ingalls Shipbuilding in Gulfport, Miss. — the only other Navy supplier of the Arleigh Burke-class guided missile destroyers — was awarded contracts to build five ships.

Full funding for the 10th ship — $987 million — was appropriated in fiscal year 2013, according to Collins’ spokesman Kevin Kelley, but sequestration resulted in a $304 million shortfall.

Members of Maine’s congressional delegation in June expressed frustration over the impact of the cuts, and said they would fight to ensure funding was found for a fifth BIW ship.

Collins said she expects the full Senate Appropriations Committee to approve the defense budget on Thursday, but acknowledged that because the House Defense Appropriations Subcommittee did not include funding for the ship, the ultimate decision on funding would be made by a committee of conference.

“I expect to be a member” of that committee, she said.

Bath Iron Works is slated to build one destroyer in fiscal years 2013, 2015, 2016 and 2017.

Chris Johnson, spokesman for Naval Sea Systems Command in Washington, D.C., told the Bangor Daily News at the time that Ingalls was slated to build the only DDG 51 in 2014, but that if Congress could resolve its funding shortfall, the second ship would be awarded.

Collins said Tuesday that the funding is “absolutely critical to Bath Iron Works because it will allow the Navy to award a contract for a DDG 51 to Bath Iron Works … it will help keep BIW employees building ships and will avoid hundreds of layoffs that otherwise would have occurred.”