In what might be the most significant pressure put on Washington Redskins owner Daniel Snyder to change his team's name, the United States Patent and Trademark Office has canceled the team's trademarks on the basis that it is "disparaging to Native Americans."

In its 2-1 ruling issued on Wednesday, the Trademark Trial and Appeal Board, an independent tribunal within the USPTO, wrote that it was charged with determining only whether the trademark was offensive to the people it referenced, not the entire U.S. population. Five Native Americans, representing four tribes, brought the case against the league in 2006.

Although the Redskins name and past logos are involved in the decision, the trademarks that were canceled do not include the current Redskins logo.

"Petitioners have found a preponderance of evidence that a substantial amount of Native Americans found the term Redskins to be disparaging when used in connection with professional football," the ruling said. "While this may reveal differing opinions with the community, it does not negate the opinions of those who find it disparaging."

The ruling does not force the NFL or Snyder to change the name, but trademarks registered between 1967 and 1990 will no longer be protected under federal law if the NFL and the Redskins lose an appeal to the U.S. District Court.

Bob Raskopf, the trademark attorney for the Redskins, said the team will appeal Wednesday's ruling and is confident the court will successfully overturn it. He noted that the team's trademark registrations will remain valid while the case is appealed.

"We are confident we will prevail once again, and that the Trademark Trial and Appeal Board's divided ruling will be overturned on appeal. This case is no different than an earlier case, where the Board cancelled the Redskins' trademark registrations, and where a federal district court disagreed and reversed the Board," Raskopf said in a statement.

In 1999, a panel ruled to cancel the trademarks after a battle with Native American groups. The decision was later overturned on a technicality after the court decided that the plaintiffs were too old and should have filed their complaint soon after the Redskins registered their nickname in 1967.

"The evidence in the current claim is virtually identical to the evidence a federal judge decided was insufficient more than ten years ago. We expect the same ultimate outcome here," Raskopf said in his statement.

Sen. Maria Cantwell, D-Wash., told ESPN.com that she expects Wednesday's ruling to be upheld on appeal.

"This puts a big dent in their business model of trying to gain revenue from a disparaging term of slur," she said. "I find it very unlikely that someone is going to overrule the patent office on this. This is a huge decision by a federal agency."

Cantwell, with Senate Majority Leader Harry Reid, wrote a letter signed by 49 Democratic senators last month that encouraged a name change. She said that if the Redskins and the league refuse to change the name, there are many options available for the Senate, including perhaps ridding the league of its tax-exempt status.

Reid also applauded the decision.