The head of the Environmental Protection Agency said that he, and not President Bush, made the final decision on issues involving global warming and air quality.

"The president provided input," said EPA Administrator Stephen Johnson, referring to new ozone standards issued in March, before the House Oversight and Government Reform Committee Tuesday. "Ultimately, I made the decision."

Johnson rejected Democratic criticism that he submitted to White House pressure to reverse his positions on decisions.

"It's been a very transparent process," he said.

Representative Henry Waxman, the panel's chairman, questioned the legality of White House involvement in EPA rulings ranging from new ozone standards to the rejection of a request by California to establish its own auto emissions standards tougher than federal regulations.

Democrats have alleged that Johnson considers politics before science. Waxman, a California Democrat, released two memos before the hearing that suggested Johnson, a 27-year EPA veteran, went against views he and other scientists agreed upon to accommodate White House requests.

Republican Representative Darrell Issa of California said there is nothing wrong with a president's making policy decisions.

"Within the limits of lawful discretion, a president, any president, may choose among a variety of policy options," he said. "It should not be surprising that the policy option chosen by a president of one party differs from the policy option that a member of Congress from another party would have chosen."