It will take an act of Congress or a massive fundraising effort to keep the Draken Harald Hårfagre on its American voyage, which includes a stop this summer in Duluth.

The U.S. Coast Guard says it doesn't have the authority to give the world's largest Viking ship an exemption from a law that requires all ships navigating the Great Lakes under a foreign flag to have a pilot on board. Only Congress could do that.

Short of an emergency meeting to pass such a resolution, the efforts to get the Draken to Tall Ships Duluth 2016 and similar events in Green Bay, Wis., and Chicago will come down to raising about $400,000 to cover pilot fees, said Sarah Blank, a spokeswoman for the Draken who is traveling with the ship.

The Draken found enough money to hire a pilot to get from Detroit to Bay City, Mich., in time for this weekend's Tall Ships event, but the ship will be anchored there unless fundraising efforts in Norway or in cities eagerly awaiting its arrival can find more money in their budgets to help cover the cost.

"The crew will be devastated if we can't keep sailing," Blank said Wednesday. "We twisted and bent our budget to get to Bay City. We didn't think it would be right to not go to Bay City just three days before the event. We hope to continue the expedition."

To do that, however, "we need a plan and know that we have enough in our budget to make it," she continued.

Fans following the Draken's progress as it made its way across the Atlantic from Norway and through the St. Lawrence Seaway unwittingly tipped off the Coast Guard through social media posts. Some posts, which referenced that the Draken has been given an exemption to the pilot rule, drew the attention of the Coast Guard, which caught up with the ship as it entered U.S. waters in Lake Erie.

The Great Lakes Pilotage Act of 1960 states that, except for recreational boats, all foreign vessels on the U.S. side of the Great Lakes — cargo or not — must have a pilot. A Canadian law, however, allows an exemption for ships that are shorter than 35 meters. The Draken checks in at 34.5 meters (115 feet). Black said the Draken had met with both U.S. and Canadian officials, and had thought the Draken would be in the clear.

"We had information from all kinds of sources and thought we were exempted from pilot fees," she said. "We got information that we didn't need a pilot. That was wrong. Of course, we would have investigated this further."

It's possible the mix-up resulted because there are lots of laws with reciprocity between the two nations, but not in this case, said Lorne Thomas, chief of external affairs for the Coast Guard's Ninth District in Cleveland, which oversees the Great Lakes.

"The 56-year-old law has applied for every Tall Ship event in the Great Lakes, and we are pretty confident they were informed they needed pilotage," Thomas said. "They received accurate information from Canada, but essentially extended that to apply to U.S. waters, and that is the crux of the issue. The perception is that the Coast Guard granted a waiver and then retracted it. We never administered an exception. It is the law, and we have no discretion."

There is no such problem for the El Galeon Andalucia, a Spanish ship heading to the Duluth event in August. It did secure a pilot, who can run as high as $400 per hour. Thomas said Draken officials are not upset with the idea of having a pilot, "just the fee," he said.

Supporters have started an online petition at calling for the fees and pilot requirement to be waived. The petition had more than 9,500 electronic signatures by Wednesday evening.

Calling the Draken "one of the stars of the show with an amazing history to be told," Tall Ships Duluth executive producer Craig Samborski said it would be "disappointing" if the ship built to recreate the transatlantic crossing made by explorer Leif Eriksson more than 1,000 years ago didn't make it to Duluth.

The Draken, which features an oak hull and a 3,200-square-foot sail, carries a crew of 32 under the command of Björn Ahlander.

On Tuesday, Samborski said the ship's scheduled appearance has helped drive ticket sales. While he declined to say how many tickets have been sold, "we are about double of 2013," he said. The goal for 2016 is 300,000 visitors.

The ship is named after Harald Fairhair, the king who unified Norway into one kingdom. Construction on the ship began in 2010. Built with techniques from archaeological findings, using old boatbuilding traditions and the legends of Viking ships from the Norse sagas, the Draken is believed to be the largest Viking ship built in modern times, according to its website.

Duluth's festival runs Aug. 18-21.

"We want to come and visit," Blank said. "Right now, the answer is I don't know."