The lawyer told the Atlanta court 41-year-old Terri Schiavo might die before they could get a chance to fully argue their case.
A federal judge earlier rejected a bid by her parents to have the tube reconnected to prevent her death.
Federal district court judge James Whittemore ruled that Florida state courts had not violated her rights by ordering her feeding tube to be disconnected.
“Theresa Schiavo’s life and liberty interests were adequately protected by the extensive process provided in the state’s courts,” he ruled.
President George W. Bush and Republican leaders who have led a political campaign to keep Ms Schiavo alive expressed disappointment at the judge’s decision, which came four days after her feeding tube was removed after a Florida state court ruling.
“We would have preferred a different ruling,” White House spokesman Scott McClellan said.
“My understanding is that the lawyers for the parents are now appealing,” Mr McClellan added. “We hope that they will be able to have relief, through the appeals process. We continue to stand on the side of defending life.”
Terri Schiavo has been in a persistent vegetative state for 15 years since heart failure caused several brain damage.
Her husband, Michael Schiavo has fought a seven-year legal battle for her right to die.
On Friday a Florida state court ordered her feeding tube be removed so that she be allowed to die.
Ms Schiavo’s family believe she should be kept alive and they took their case to Washington.
Tom DeLay, leader of the Republican majority in the House of Representatives and one of the architects of special legislation passed at the weekend to help the family make an appeal to a federal court, called the federal judge’s ruling “disheartening”.
“This decision is at odds with both the clear intent of Congress and the constitutional rights of a helpless young woman,” Mr DeLay said.
“As long as there’s still a chance to save Terri, this fight is not over,” he added.
Michael Schiavo says his wife told him prior to her disability that she would never want to be kept alive artificially and has expressed outrage at the Congress interference in the case.