TRAVERSE CITY, Mich. — Six attorneys general in the Great Lakes region called for a multi-state coalition Wednesday that would push the federal government to protect the lakes from invasive species such as Asian carp by cutting off their artificial link to the Mississippi River basin.

In a letter obtained by The Associated Press, the officials invited colleagues in 27 other states to join a lobbying campaign to separate the two watersheds, contending they have as much to lose as the Great Lakes do from migration of aquatic plants and animals that can do billions in economic damage and starve out native species.

“We have Asian carp coming into Lake Michigan and zebra mussels moving out of the Great Lakes and into the heart of our country, both of which are like poison to the ecology of our waters,” Michigan Attorney General Bill Schuette said. “This is not just a Great Lakes issue. By working together, we hope to put pressure on the federal government to act before it’s too late.”

Also signing the appeal were attorneys general from Minnesota, New York, Ohio, Pennsylvania and Wisconsin. It was being sent to their counterparts across the Mississippi basin as well as Western states such as Nevada, where Lake Mead and other waterways have been infested by zebra mussels believed to have been transported from the Great Lakes by unwitting recreational boaters.

Five of the Great Lakes states are suing the Army Corps over its operation of a Chicago-area waterway network that creates an artificial pathway between Lake Michigan and the Illinois River, a Mississippi River tributary. Bighead and silver carp, natives of Asia, have advanced up both rivers and are in Chicago Sanitary and Ship Canal, where the Army Corps operates electric barriers about 25 miles from Lake Michigan to prevent species migration.

DNA from the carp has been detected beyond the barriers, raising fears that some of the large, voracious fish might be getting through, although just one has been caught.

The Army Corps and other agencies are studying the barriers’ effectiveness and monitoring the waterways for the presence of carp while conducting a long-range study of how best to prevent species migrations between the two drainage basins. Among the options is severing the link created more than a century ago by reversing the flow of the Chicago River and constructing the canal.

But the study isn’t scheduled for completion until 2015, and it could take many additional years to reconstruct the waterway. In their lawsuit, the states demand a quicker timetable.

Schuette said the attorneys general weren’t asking their colleagues in other states to join the lawsuit, but to help ratchet up the pressure on the Army Corps.

“They can work with their congressional delegation, use their contacts with the Army Corps, with their governors,” he said. “We need to turn up the heat.”

Asian carp have attracted wide attention because of their size — up to 4 feet long and 100 pounds — and destructive potential. Biologists say if they become established in the Great Lakes, they could a $7 billion-a-year fishing industry by gobbling up tiny plants and animals on which the entire food chain depends.

But zebra and quagga mussels have already ravaged the lakes, and the Army Corps this summer released a list of 40 other invasive species with a high potential of slipping between the Mississippi and Great Lakes basins. Of those, 30 threaten to enter the Mississippi watershed.

“Invasive species … are a potential hazard to every waterway and every state in the country,” Pennsylvania Attorney General Linda Kelly said.

Maj. Gen John Peabody, commander of the Army Corps’ Great Lakes and Ohio River Division in Cincinnati, declined direct comment on the letter, but said his organization will continue collaborating with others involved in fighting to block the Asian carp’s spread.

“The Corps of Engineers remains committed to working with all federal, state and local partners to aggressively advance our successful efforts to contain the Asian carp below the fish barrier system, as well as to address long-term measures to prevent the spread of aquatic nuisance species between the Great Lakes and Mississippi River Basins,” Peabody told The Associated Press.

Officials with the Corps have said repeatedly they could not speed up the study because of the complex scientific and engineering issues involved. It’s examining dozens of potential aquatic pathways, not just the Chicago area.

“The Corps welcomes the active involvement of all stakeholders, especially state authorities, in the development of the Great Lakes and Mississippi River Interbasin Study,” Peabody said.