LANSING, Mich. (AP) — Michigan's attorney general pledged Monday to move to shut down an oil pipeline in the Great Lakes if the governor doesn't find a "swift and straightforward" resolution to the contentious issue.

Gov. Gretchen Whitmer last month halted state agencies' work to facilitate construction of a tunnel beneath the lakebed to house a new segment of Line 5 in the channel where Lakes Huron and Michigan meet, pointing to a legal opinion from Attorney General Dana Nessel while citing concerns that her Republican predecessor's plan would keep the existing 66-year-old pipeline in the water too long. But the Democrat said this month she was open to still building the tunnel . Her administration is in talks with pipeline owner and operator Enbridge.

"I respect the Governor's effort to find a swift and straightforward resolution to this issue, but if unsuccessful I will use every resource available to our office to shut down Line 5 to protect our Great Lakes," Nessel, a Democrat who promised during her campaign to close the pipeline, said in a short statement.

A spokeswoman later said while Nessel was reluctant to impose a specific deadline on Whitmer's efforts with Enbridge, she was hopeful that the governor by June 1 would have a plan for decommissioning Line 5.

"The Attorney General shares the Governor's sense of urgency to remove the pipeline from the Great Lakes at the earliest possible moment," said Kelly Rossman-McKinney.

Nessel released an opinion last month saying a law enacted in December to implement former Gov. Rick Snyder's tunnel deal is unconstitutional.

As a candidate, Nessel said she would seek a court injunction to shut the pipeline by alleging that Enbridge violated a 1953 state easement. Although the federal government regulates oil pipelines, Michigan owns the lake bottom and granted the easement allowing the pipeline to go there.

Line 5 carries about 23 million gallons (87 million liters) of crude oil daily between Superior, Wisconsin, and Sarnia, Ontario. The underwater segment that traverses the Straits of Mackinac is divided into two side-by-side lines.

Environmental groups contend that the segment is a spill hazard and should be decommissioned. The company says it is in good shape and could operate indefinitely. The pipeline project is supported by labor organizations friendly to Whitmer because of the jobs it would create.

"We believe the tunnel project is the best way to protect the waters of the Great Lakes while ensuring families, manufacturers and other businesses safely receive the energy transported through Line 5," said Enbridge spokesman Ryan Duffy. "We continue to provide information to the Governor's office and to seek clarification from the Administration on a path forward for the tunnel project."

Nessel does not believe a tunnel is the best or safest way to meet Michigan's energy needs, including the delivery of propane to the Upper Peninsula, but she is not engaged in the policy-oriented negotiations that Whitmer and lawmakers may be having, said Rossman-McKinney. She supports a proposal that Whitmer appoint a task force to address concerns about supplying heat to the U.P.

"The AG's prospective involvement in decommissioning Line 5 concerns the hazards posed to the Great Lakes, not whether the use of oil pipelines in general makes for sound energy policy," Rossman-McKinney said.