The Senate Environment and Public Works Committee canceled a vote to subpoena the EPA administrator after Republicans boycotted the meeting Thursday.

Under committee rules, two Republicans must be present in order to achieve a quorum.

Chairwoman Barbara Boxer, D-Calif., is seeking a draft document the Environmental Protection Agency prepared late last year that found greenhouse gas emissions endanger public welfare. The EPA draft was part of a response to a 2007 Supreme Court decision that found greenhouse gases were pollutants under the Clean Air Act. If the EPA decides emissions endanger the public, the next step would be regulations to limit those emissions.

The EPA forwarded the document to the White House in an e-mail in December. The White House refused to open the document and asked EPA officials to retract it. The EPA recently decided to seek comment on greenhouse gas regulations but is unlikely to move forward under this administration.

Boxer said the quashed EPA draft was the strongest official statement she has seen on the dangers of global warming.

“It recounts, point by point, the unequivocal evidence for global warming, and the growing list of the impacts unchecked global warming will have on our people and on every region of our country,” Boxer said.

Republicans object to the subpoena. The panel’s ranking Republican, James M. Inhofe of Oklahoma, called it “unwarranted and not focused on true oversight.”

He said Boxer’s actions were “a political exercise that is intended  . . .  to help keep this issue of alleged administration interference alive in the press as long as possible.”

The White House this week allowed Boxer and other senators to review the document and take “reasonable notes,” but they could not distribute it or make copies. White House officials were present when Senate staff reviewed the document.

Even if the committee did find the votes for a subpoena, the White House likely would assert executive privilege and refuse to hand over the document. The Bush administration recently did just that when Rep. Henry A. Waxman, D-Calif., requested separate EPA documents.