TRAVERSE CITY, Mich. AP) _ Michigan asked the U.S. Supreme Court on Monday to sever a century-old connection between the Great Lakes and the Mississippi River system to prevent Asian carp from invading the lakes and endangering their $7 billion fishery.

State Attorney General Mike Cox filed a lawsuit with the nation's highest court against Illinois, the U.S. Army Corps of Engineers and the Metropolitan Water Reclamation District of Greater Chicago. They operate canals and other waterways that open into Lake Michigan.

Bighead and silver carp from Asia have been detected in those waterways after migrating north in the Mississippi and Illinois rivers for decades.

Officials poisoned a section of the Chicago Sanitary and Ship Canal this month to prevent the carp from getting closer to Lake Michigan while an electrical barrier was taken down for maintenance.

But scientists say DNA found north of the barrier suggest at least some of the carp have gotten through and may be within 6 miles of Lake Michigan. If so, the only other obstacle between them and the lake are shipping locks and gates, which open frequently to grant passage for cargo vessels.

The lawsuit asks for the locks and waterways to be closed immediately as a stopgap measure, echoing a call by 50 members of Congress and environmental groups last week. But the suit goes further, also requesting a permanent separation between the carp-infested waters and the lakes.

That would mean cutting off a link between the Mississippi and Great Lakes basins created more than 100 years ago, when Chicago reversed the flow of the Chicago River and began sending sewage-fouled Lake Michigan water south toward the Mississippi River.

"The Great Lakes are an irreplaceable resource," Cox, who is seeking the Republican gubernatorial nomination in Michigan, said at a news conference in Detroit. "Thousands of jobs are at stake and we will not get a second chance once the carp enter Lake Michigan."

He likened the notorious fish to "nuclear bombs." The biggest Asian carp can reach 4 feet in length and weigh 100 pounds while consuming up to 40 percent of their body weight daily in plankton, the base of the Great Lakes food chain.

Cox went directly to the Supreme Court because it handles disputes between states.

Michigan is seeking to reopen a case dating back to 1900, when Missouri filed suit against Chicago over its re-engineering of the river.

After that issue was resolved, several Great Lakes states _ including Michigan _ renewed the suit with a new complaint: Chicago's diversion of water away from the basin was harming the lakes by lowering water levels.