Initial steps to close the breach on Fire Island started Thursday, but state officials said they did not formally request a closure.
The letter came a day after Suffolk County Executive Steve Bellone and other local officials demanded the DEC, Fire Island National Seashore and Army Corps close the breach, citing unprecedented flooding along the South Shore.
Environmentalists say it's too early to know if increased flooding is connected to the gap superstorm Sandy created.
Bellone spokeswoman Vanessa Baird-Streeter said the county appreciated the state taking initial steps. Bellone "believes the breach should be closed as quickly as possible," she said.
Army Corps spokesman Chris Gardner said any physical work couldn't be undertaken for months because the agency must determine the amount of work needed and availability of equipment, and comply with environmental regulations that may limit the time of year the work can take place.
The state would share the costs with the Army Corps, according to Martens' letter.
Rep. Tim Bishop (D-Southampton) supported the collaborative process to move forward, but was "concerned that the effects of a future major storm on the South Shore could be made worse if the breach is open when it hits," his spokesman Oliver Longwell said.
The width of the breach has fluctuated since Sandy hit Oct. 29. As of Wednesday, the north side of the breach was 696 feet wide, up from 616 feet at the end of February. On the south side, it measured 732 feet wide, down from 1,171 feet at the end of February, National Seashore records show.
Environmentalists, who have said rising sea levels along the East Coast are causing the flooding, want the breach to stay open to help clean the Great South Bay, which has been plagued by algal blooms and falling clam populations.
"We want facts not fear to be the driver," said Adrienne Esposito, executive director of Citizen Campaign for the Environment. "We can't let political science trump marine science."