The White House has told lawmakers that former Secretary of State Henry Kissinger, President Bush's choice to head a commission investigating the Sept. 11 attacks, is not required by law to disclose his business clients.
Meanwhile, former Sen. George Mitchell, D-Maine, resigned as the commission's vice chairman.
Senate Democrats want the list to determine whether Kissinger's clients pose conflicts of interests.
A White House official, speaking on condition of anonymity, said federal law guiding presidential appointments does not require such disclosures when the appointee is not paid. Kissinger is drawing no salary.
The New York Times reported the White House counsel's office obtained an opinion from the Justice Department's Office of Legal Counsel supporting the White House position.
"It is our hope this will be resolved through continued discussion, not political grandstanding," a White House official told the paper.
The law does not prohibit Kissinger from turning over the client list on his own. The former secretary of state has not commented on what he might do.
Senate Democratic aides insist the laws cover Executive Branch appointees, whether they are paid or not.
The confrontation came to a head as Mitchell resigned from the commission, citing a lack of time, but also a lack of money.
"I have concluded that the work of the commission would require more time than I anticipated and more than I now can commit to," Mitchell wrote in a letter to Democratic congressional leaders.
Former Rep. Lee Hamilton, D-Ind., will replace Mitchell as vice chairman of the National Commission on Terrorist Attacks.
"As you know, some have urged that I sever all ties to the law firm with which I am associated," he wrote. "Since I must work to support my family, I cannot comply."
He said concerns were raised about potential conflicts of interests and whether he would devote the time necessary to the commission. Some politicians and commentators have raised similar questions about Kissinger, who leads a major consulting firm.
Mitchell said his legal work would not have posed a conflict, but he was concerned about how much time the commission would have demanded.
His replacement, Hamilton, served more than 30 years in the House and is a former chairman of the International Relations and Intelligence committees.
The commission will follow up the work of the congressional inquiry that issued its final report Wednesday on intelligence failures leading up the terrorist attacks. The commission will conduct a broader investigation, looking at issues beyond intelligence, including aviation security and immigration.
It will be made up of five Democrats and five Republicans, including Kissinger, who was appointed by President Bush.
Democratic leaders on Wednesday appointed four other members to the panel: outgoing Sen. Max Cleland, D-Ga., outgoing Rep. Timothy Roemer, D-Ind., attorney Richard Ben-Veniste, and Jamie Gorelick, a deputy attorney general in the Clinton administration.
On Tuesday, Senate Republican leader Trent Lott appointed former Sen. Slade Gorton, R-Wash. Republican congressional leaders will name three more members.
Gorton's appointment has disappointed some relatives of the Sept. 11 victims. Gorton, a former chairman of a Senate aviation subcommittee, had close ties with Boeing Co., the largest private employer in Washington state. Boeing made all four planes used in the attacks.
Gorton's law firm, Seattle-based Preston Gates Ellis, also represents several major airlines.
"I think Gorton is a terrible appointment," said Stephen Push, whose wife, Lisa Raines, died in the attack on the Pentagon.
Kristen Breitweiser, whose husband Ronald was killed in the World Trade Center, said Gorton's appointment follows a troubling pattern set by the selection of Kissinger. Family members have criticized Kissinger's appointment because of potential conflicts.
"We want this commission to be independent — to fix problems that became apparent Sept. 11," said Breitweiser, of Middletown, N.J.
Gorton did not return messages left at his offices in Seattle and Washington.
President Bush initially opposed the independent commission, but eventually agreed to back it as support grew in Congress. The panel's makeup and rules were the result of long negotiations between lawmakers and the White House, each accusing the other side of trying to manipulate the panel for partisan reasons. The final report will be due less than six months before the 2004 presidential elections.