Biographer and filmmaker David DeJonge said the service for Frank Buckles is set for , but it's unclear who can attend.
"The family is trying to get answers," he said in an e-mail. "The family desires every American and foreign organization an ability to pay respects and recognize the passing of the generation."
Cemetery spokesman Jennifer Lynch declined comment.
"Out of respect for the Buckles family, we are deferring all comment to the family until such time as they believe it is appropriate for us to inform the media of their plans," she said.
President Barack Obama has already ordered that
Susannah Flanagan wanted her father, the last of the so-called Doughboys, to lie in repose in the U.S. Capitol, but Congress failed to approve that plan. Politicians remain divided over how to best honor Buckles and the 4.7 million other Americans who served in that war.
The last person to lie in the Capitol rotunda was President Gerald Ford. The honor is reserved mostly for elected and military officials, but others have included civil rights activist Rosa Parks and unknown soldiers from both World Wars and the Korean War.
A great-grandson of Sir Winston Churchill, Jonathan Sandys, entered the fray Thursday, issuing a statement that called on Congress to allow the use of the rotunda.
He urged the public to join him in insisting that Buckles be afforded the honor "beginning this Sunday, as a mark of respect and as a representation of thanks to his entire generation from a grateful nation."
Buckles enlisted at 16 after lying about his age. Born in
He died last month on his farm in Charles Town, nearly a month after his 110th birthday.
Buckles had devoted the last years of his life to campaigning for greater recognition for his former comrades, prodding politicians to support a national memorial in
Only two known WWI veterans remain - 110-year-old survivors Florence Green in