NEW YORK -- The U.S. Patent Office has canceled six trademarks belonging to the Washington Redskins football team, saying they are offensive to Native Americans.

In a 2-1 decision released Wednesday, the office's Trademark Trial and Appeal Board ruled that "these registrations must be canceled because they [are] disparaging to Native Americans."

The Patent Office said it will continue to treat the trademark registrations as though they are valid while the team appeals the decision. The team has said it will appeal, a process could take years.

In the meantime, the Redskins can continue to use the logos.

But if the decision is upheld,it will be hard for the team to claim ownership of its brand. If it wants to go to court against a counterfeiter making T-shirts with the team's logo, for instance, it will be harder to show that the organization owns the brand. The team will have to illustrate that they have always used the logos, rather than relying official trademark registrations.

The decision came in response to a suit brought by five Native Americans.

"We are extraordinarily gratified to have prevailed in this case," Alfred W. Putnam, Jr., Chairman of Drinker Biddle & Reath LLP, which represented the five men and women, said in a statement.

The team has faced mounting pressure in recent years to ditch its name altogether, which is considered a slur against Native Americans. In May, 49 senators, including Majority Leader Harry Reid, signed a letter to NFL Commissioner Roger Goodell saying that the "team is on the wrong side of history" and he should endorse a name change. A week later, a coalition of 77 tribal, civil rights and religious groups, including the National Congress of American Indians and the NAACP, signed a letter urging players to join a campaign to change the team's mascot.

The Patent Office also canceled the registrations in 1999, but a federal judge overturned that decision in 2003, saying there was no proof that the name was disparaging at the time of registration. Some of the trademarks date back to the 1960s.

In a statement put out by the team, its trademark attorney, said he believed this decision, like the previous one, would be overturned.

"We've seen this story before," the attorney, Bob Raskopf, said. "And just like last time, today's ruling will have no effect at all on the team's ownership of and right to use the Redskins name and logo."

He said the team would appeal.

The Patent Office has occasionally denied trademark registrations deemed to be disparaging in the past, and even canceled existing ones. But today's ruling against the Washington, D.C. team was unique given how old and visible the Redskins brand is, according to Tim Bukher, an intellectual property lawyer at Thompson Bukher LLP in New York City.

"It's a 50-year-old asset of a major NFL team," Bukher said. "I imagine it's a pretty big hit resource-wise."

The structure of the NFL, which distributes profits from licensing among the teams, could help mitigate any loss to the Redskins, Bukher said.