Environmental groups that have been the biggest critics of President Bush his first seven months in office said Monday that in light of the terrorist attacks they are pulling advertisements and withholding statements that criticize his policies.

"In deference to the fact that we need to pull together as a nation, we're not going to be making any kind of statements on the issues at this point," said Elliott Negin, communications director for the Natural Resources Defense Council.

"We want to show our support for the administration. This was a heinous act and it's unseemly for anyone to try to exploit this tragedy by pushing a pre-existing agenda. So we're basically just sitting tight," he said.

NRDC pulled an ad urging the administration to lower arsenic standards for drinking water and started posting Web site information on relief efforts. Other groups, such as the Sierra Club, sent memos to staff telling them to stop criticizing Bush publicly. The Sierra Club also pulled television, radio and print ads, shut down phone banks and removed Internet material seen as critical of Bush.

The two groups along with other environmentalists had been gearing up for Senate action on an energy package. They say how long they will sit on the sidelines depends largely on what Congress does.

Jennifer Ferenstein, president of the Sierra Club, said it took her group just minutes to step back, shift focus and immediately cancel an annual meeting in San Francisco the week of the attacks. The group also urged its members not to do anything disrespectful, she said.

"Out of common decency and respect right after it happened, we made the decision it wasn't appropriate to distract the American public at this time," said Ferenstein. "But the environment will still always be important. Whatever steps we taking in responding to terrorist violence, we need to think about protecting our environment because that's an American value."