Carnival Cruise Lines announced plans Thursday to leave the port of Baltimore, a move that could cost the region scores of jobs and millions in economic activity generated by big-spending passengers and businesses servicing the ships.

The Miami-based company said that without federal approval of its plan for curbing air pollution, it would cut back on the number of cruises and move the Pride to a dock in Tampa, Fla., in November 2014. The Pride, a 2,124-passenger ship, sails weekly from Baltimore to the Bahamas and Caribbean.

The move would leave the city with one other large cruise ship, Royal Caribbean's Grandeur of the Seas, still sailing regularly from the South Locust Point terminal. It also left state officials, who had been lobbying the Environmental Protection Agency on Carnival's behalf, scrambling to prevent such a blow to the cruise industry here.

The Pride's departure puts on hold preliminary discussions by port officials about expanding cruise facilities in Baltimore, said Richard Scher, spokesman for the port administration. The two cruise lines now support 220 jobs and pump $90 million into the economy, according to state officials.

"We're going to fight real hard to get them back," James White, executive director of the Maryland Port Administration, said of Carnival. But he also said he's trying to lure another cruise line here just in case.

Carnival spokesman Vance Gulliksen said that while the Pride's sailings from Baltimore have been "very successful," uncertainty over how to comply with a pending air quality regulation forced the company to make "itinerary changes" as it considers its options.

Gulliksen said the company would "evaluate all viable options" for returning to Baltimore. Pride voyages from Tampa are scheduled only through April 2015.

All oceangoing ships, including cargo and cruise vessels, are required by the International Maritime Organization to burn cleaner, low-sulfur fuel when within 200 nautical miles of the U.S. and Canadian coasts. Ships are supposed to use an even cleaner fuel with 90 percent less sulfur starting in 2015.

The EPA contends that the ship emission limits will prevent thousands of premature deaths nationwide. The agency also argues that such limits will save millions in health care costs for treating respiratory problems associated with massive amounts of fine particle pollution and smog-forming gases emitted by oceangoing vessels now burning low-grade "bunker" fuel.

The low-sulfur fuel would still be many times dirtier than the diesel now used by trucks and buses, the EPA notes.

But cruise industry officials have warned that they would be forced to cut back sailings or relocate ships because of the higher costs associated with having to burn cleaner fuel.

According to Maryland port officials, the more costly fuel would add $65 to $140 per passenger to fares on voyages from Baltimore to Bermuda, the Bahamas and Caribbean.

Carnival had offered to spend $200 million over the next three years putting pollution "scrubbers" on 59 of its ships as they went into dry dock for overhaul, according to state port officials.

EPA spokesman David Bloomgren said in an email that Carnival has been in talks with the agency and with the U.S. Coast Guard about getting a temporary exemption from having to burn cleaner fuel while it develops scrubber technology for some Carnival ships. He said the agency would not comment further as the company's request "continues to evolve" in those talks.

The company did not respond to questions about those discussions.

The Pride was scheduled for dry docking in January 2014. If the EPA approves Carnival's plan, the company would be in compliance with the new pollution limits well before they take effect, said Scher.

Gov. Martin O'Malley had called acting EPA Administrator Bob Perciasepe to urge the agency to make a quick decision. His spokeswoman said he supported Carnival's request for a waiver.

"Creating jobs and spurring economic growth is always our top priority, while also protecting the health and safety of our citizens,'' said Takirra Winfield, O'Malley's press secretary. She added that the governor hoped the Pride would return to Baltimore, and that the company would continue to work with the EPA to "maximize" their negotiations.

The EPA had asked for more information about Carnival's plan, White said. But, he said, the agency has not given the cruise line the assurances it would need to feel comfortable about going forward with installing scrubbers.

"With all the uncertainty, and Carnival having to put its schedule out a year and a half out, they had no other choice," White said.