SOUTH PORTLAND, Maine — The city on Tuesday asked a federal judge to dismiss a lawsuit filed by Portland Pipe Line Corp., on grounds the company has no actual plans to move Canadian tar sands crude oil through its pipeline to South Portland.

The motion was the city’s first official response to the lawsuit filed Feb. 6 in U.S. District Court in Portland by PPL and American Waterways Operators, a trade group for tugboat and barge operators.

The lawsuit seeks to overturn the city’s Clear Skies Ordinance, passed by the City Council last July. The ordinance is a collection of zoning amendments prohibiting PPL from reversing the flow of crude oil that is now piped from South Portland to Montreal.

The three-page motion, accompanied by 103 pages of supporting documents, claims the plaintiffs “have not alleged any current or concrete plans to undertake any activity that might plausibly fall within the scope of the zoning ordinance amendments.”

It also says the act of prohibiting the exportation of crude oil from Canada to Portland Harbor is technically not being infringed upon, which is what PPL claims in its lawsuit.

The lawsuit claims that the Clear Skies Ordinance violates “multiple provisions of the U.S. and Maine constitutions, as well as federal and state statutes,” and that the city seeks to “retard, and in fact have retarded, international and interstate commerce.”

South Portland, in its motion, alleges PPL’s accusations are premature.

“Indeed, in the proper legal context, Plaintiffs’ claims here are not merely unripe; the seeds have not even been sown,” the city’s lawyers said.

The company has had permits to reverse the pipeline flow, but those permits have expired or were surrendered.

The Clear Skies Ordinance was passed after voters in November 2013 narrowly defeated a broader referendum that would have banned the export of crude oil from South Portland.

Backers of the ordinance have said tar sands — actually diluted bitumen — presents too much of an environmental threat in the way it is produced and transported, and in the event of a spill or pipeline leak.

Opponents have argued it puts too much city tax revenue, and too many waterfront jobs, at risk.