TRAVERSE CITY, Mich. (AP) — The Obama administration Tuesday opposed Michigan and other states that want to close shipping locks near Chicago to prevent ravenous Asian carp from invading the Great Lakes.

Solicitor General Elena Kagan told the U.S. Supreme Court that heeding the states’ request would endanger public safety while disrupting cargo and passenger vessel traffic.

While acknowledging the carp pose a threat to the lakes and their $7 billion fishery, Kagan said it was unclear that closing the locks immediately was necessary to keep them out.

“In a host of ways, the federal government has demonstrated its commitment to protecting the Great Lakes from the expansion of Asian carp,” she said in a written memo. “Nothing in federal law warrants second-guessing its expert judgment that the best information available today does not yet justify the dramatic steps Michigan demands.”

Michigan Attorney General Mike Cox filed a lawsuit with the nation’s highest court last month. It asked that several locks on waterways south of Chicago be closed immediately as a first step toward eventually severing a century-old artificial link between the Great Lakes and the Mississippi River basin.

The waterways, including the Chicago Sanitary and Ship Canal, are infested with bighead and silver carp that have been migrating northward in the Mississippi and Illinois rivers for decades. They can grow up to 4 feet long and 100 pounds and are notorious for starving out other fish species.

Officials poisoned a section of the canal in December after discovering genetic material that suggested at least some carp had eluded an electric barrier and could be within 6 miles of Lake Michigan. If so, the only other obstacles between them and the lake are shipping locks and gates.

Minnesota, New York, Ohio and Wisconsin and the Canadian province of Ontario have filed documents supporting Michigan’s position.

Illinois, named as a defendant in the lawsuit along with the U.S. Army Corps of Engineers and a Chicago agency, submitted papers Tuesday saying Michigan had not made a convincing case for an immediate court order.

Kagan said closing the locks would require using more expensive means to haul coal and other commodities between the lakes and the Mississippi River system. Switching to land transportation would cost shippers nearly 10 percent of their cargo’s total value, she said.

The locks also provide essential access for Coast Guard crews responding to recreational boating emergencies and environmental crises such as oil spills in the waterways, Kagan said.

She contended there was insufficient evidence that enough carp had slipped past the electric barrier to pose an imminent danger.

Michigan officials say any economic losses from closing the locks would be small in comparison to the damage a carp invasion would wreak on the lakes.

John Selleck, spokesman for Cox, said Michigan officials had hoped the federal government “would agree that the status quo is putting the Great Lakes at great risk. We must act now to ensure that thousands of jobs and our greatest natural resource is protected.”