ABOARD AIR FORCE ONE — President Bush is trying to calm Americans’ outrage over soaring gas prices by ordering an investigation into whether the price of gasoline has been illegally manipulated, his spokesman said Monday.

During the last few days, Bush asked his Energy and Justice departments to open inquiries into possible cheating in the gasoline markets, said White House press secretary Scott McClellan. Bush planned to announce the action Tuesday during a speech in Washington.

Bush is under pressure to do something about gas prices that have reached nearly $3 a gallon. In a new CNN poll, 69 percent of respondents said gasoline price increases had caused them personal hardship. Other polls suggest that voters favor Democrats over Republicans on the issue, and President Bush gets low marks for handling gas prices.

House Speaker Dennis Hastert, R-Ill., and Senate Majority Leader Bill Frist, R-Tenn., urged Bush in a letter Monday to order a federal investigation into any gasoline price gouging or market speculation. Senate Democratic leader Harry Reid of Nevada dispatched his own letter, calling for a multi-pronged approach to restrain gas prices. Among the steps were swift enactment of anti-price gouging legislation, an appeal to oil companies to refrain from further price increases; use of more alternative fuels and increased attention to existing fuel-saving laws and regulations.

Bush was working on the speech aboard Air Force One as he flew home Monday evening from a four-day trip to California that ended with a swing through Las Vegas. McClellan outlined part of the speech to reporters traveling on the plane.

McClellan said Bush also will announce that his attorney general and Federal Trade Commission will send a letter to all 50 state attorneys general, who have primary authority over price gouging, to remind them to stay on top of the issue and offer federal help to do so. And he will call on energy companies to reinvest their profits into expanding refining capacity, developing new technologies and researching alternative energy sources.

“I think you’ll hear the president say very clearly that he will not tolerate price gouging,” McClellan said. Bush has consistently said that gas prices are high because global demand is rising faster than global supply and that the problem cannot be solved overnight. McClellan said Bush will talk about how experts predict that the price is expected to increase this summer and how the switch to a summer fuel mix is contributing to the problem.

Bush’s actions are part of a four-part plan to address gas prices in the short- and long-term, McClellan said. The steps McClellan outlined are:

1. making sure consumers and taxpayers are treated fairly;

2. promoting greater fuel efficiency;

3. boosting gasoline supply at home;

4. aggressive long-term investment in alternative fuels.