(CNN) -- The Iroquois Nationals lacrosse team is still being denied entry into the United Kingdom, even after the U.S. State Department granted the players a waiver to travel under their own passports Wednesday.
Secretary of State Hillary Clinton made the decision to give the team a "one-time-only waiver" to travel under their Haudenosaunee Confederacy passports, the official travel documents of the Iroquois, said State Department spokesman P.J. Crowley.
But a British Border Agency representative said later, "We would be pleased to welcome the Iroquois Nationals Lacrosse Team, but like all those seeking entry into the U.K., they must present a document that we recognize as valid to enable us to complete our immigration and other checks."
If the team members present the Haudenosaunee, or Iroquois, passport, they would have to do so "in conjunction with a U.S. or Canadian passports if they wish to seek entry to the U.K.," said the representative, who declined to be named in line with government policy.
Tonya Gonnella Frichner, legal adviser to the Iroquois Nations, said the agency's decision is "devastating."
Team officials have been in touch with World Lacrosse Championship organizers, who are working to help resolve the matter, she said, but the team's first scheduled game is Thursday evening, and it will have to be forfeited if the team doesn't appear.
The team was supposed to leave the United States Sunday for the World Lacrosse Championships, which begins Thursday in Manchester, England. However, the British Consulate told team officials last week that players would not be granted visas to enter England unless the U.S. State Department could confirm in a letter that they would be allowed back into the United States after the tournament, according to a statement issued by the team's board of directors.
The problem stemmed from the fact that the Haudenosaunee Confederacy passports do not conform to new security standards required for passports by the U.S. government, officials said.
"We have provided them with a travel document. It is not a U.S. passport. That remains the preferred travel document for those who are eligible," Crowley said. "It is still up to the U.K. to evaluate whether, based on that document, they will be granted a visa."
Team leaders said Wednesday that they had received their State Department clearance document and were reaching out to the British Consular Services in New York for a final decision.
On Tuesday, a British Border Agency representative said, "Only those with a valid travel document will be granted entry to the U.K. The Haudenosaunee passport is not internationally recognized as a valid air travel document."
Crowley said members of the lacrosse team who live in Canada would have to procure similar permission from the Canadian government and said the State Department had been in touch with Canadian authorities regarding the waiver it granted.
"Given the emphasis now placed on the security of travel documents, the best option for this group all along has been to procure a U.S. passport," Crowley said Wednesday.
"They have chosen not to do so, so we have looked at our authorities and found with these exigent circumstances, we have granted a one-time waiver. But in the future, yes, they will need U.S. passports to avoid a similar situation the next time they travel for any kind of international competition," Crowley added.
But Percy Abrams, executive director of the Iroquois Nationals, said U.S. passports wouldn't even be accepted at the competition, where players have to produce a passport originating from the country they are representing: the Haudenosaunee Confederacy.
Also, Abrams said, it's a matter of principle.
"We have our principles, and with that sovereignty goes the idea that our country has been accepted. We've been traveling on this for years," Abrams said during team practice Monday at Wagner College in New York.
"I think it should have been explained well ahead of time or someone should have been advised that travel requirements had changed," Abrams said when asked about the update in travel security measures.
The people of the six-nation confederacy live in upstate New York. The Iroquois territory once covered most of the northeastern United States and eastern Canada.
New Mexico Gov. Bill Richardson sent a letter to the State Department and the Department of Homeland Security on behalf of the Nationals earlier in the week.
He asked that the matter be reviewed immediately and noted that the passports have been used to travel outside of the United States since 1977 without problems.
"As a governor of a state with a significant Native American population, I know many tribes and pueblos will watch carefully how these young competitors are treated by the administration. As a signator of the U.N. Declaration on Human Rights, which includes the freedom to travel and return, I believe we have an obligation to assure these young men's rights are protected," Richardson wrote.
The last time the team traveled outside the country was in 2002, when the championship was held in Australia. The passports didn't pose a problem then, Abrams said. But Crowley acknowledged that that was before travel requirements changed.
On Monday, Nationals General Manager Ansley Jemison said that it is important for the team to play in the championship.
"These are the 'Michael Jordans' of the native communities. These are the guys that we hold on the pedestal. These are the guys we look up to," he said.
CNN's Mary Snow, Elise Labott and Meghan Rafferty contributed to this report.