"The president will announce that he has decided to lift the executive ban on oil exploration in America's outer continental shelf and he will again call on Congress to lift its legislative ban," said spokeswoman Dana Perino.
Bush's statement, set for 1:30 pm (1730 GMT) in the Rose Garden, comes roughly one month after he urged lawmakers to end the decades-old restrictions in order to reduce dependence on oil imports and offset sky-high energy prices.
The president's actions will not clear the way for drilling "because Congress needs to act as well" and then states must decide whether to allow offshore drilling, how much and where, and how to manage revenues.
"We think that this should not wait, the sooner they act, the faster we can send a signal to the market that we're serious," Perino told reporters, noting that the US Congress's August recess loomed.
"It is going to take some time, and it's not an automatic fix but this is a transition period that we will be in for quite a while and we think it's important to start now," she said.
Faced with a public outcry over soaring gasoline prices, Bush on June 18 said Congress should lift or modify its ban for the entire outer continental shelf, then he would lift his executive directive.
Under the 1981 federal moratorium, states are prohibited from allowing offshore oil and gas drilling and exploration, protecting virtually the entire Atlantic and Pacific coastlines and sections of the Gulf of Mexico.
Critics of lifting the drilling moratorium say it would jeopardize the environment and that production would take years to get up and running, and thus is not a realistic answer to the current supply crunch.
California Governor Arnold Schwarzenegger has already said he wants no drilling off his state's lengthy portion of the US west coast, and urged the country to move away from its dependence on oil.
"California's coastline is an international treasure. I do not support lifting this moratorium on new oil drilling off our coast," Schwarzenegger said in a statement.
© 2008 Agence France Presse