Democratic presidential candidate Barack Obama has pledged to seek a windfall profits tax on US oil companies if elected as he seeks to tap into Americans' anxiety over high gasoline prices.
Speaking in North Carolina at the start of a two-week focus on the economy, Mr Obama also drew a sharp contrast with Republican John McCain, his rival in the November election, accusing him of a "full-throated endorsement" of President George W. Bush's fiscal policies, including tax breaks for oil companies.
"I'll make oil companies like Exxon pay a tax on their windfall profits, and we'll use the money to help families pay for their skyrocketing energy costs and other bills," the Illinois senator said.
With Americans struggling to pay for record high $4-a-gallon gasoline, the jobless rate up and consumer confidence battered, Mr Obama is attempting to focus the general election campaign on the US economy.
A Gallup poll gave Mr Obama a mild bump in support following rival Hillary Clinton's departure from the Democratic race. It said he leads McCain 48 per cent to 42 per cent among registered voters.
The Democratic candidate renewed his call for a $50 billion stimulus package as a way to try to spur consumer spending and jolt new life into the economy, and a $10 billion fund for homeowners caught up in the housing crisis.
Mr McCain, attending a fundraising luncheon in Richmond, Virginia, said: "Americans are hurting. We need lower taxes, we need to stimulate our economy, we need to keep people in their homes."
He accused Mr Obama of wanting to raise the capital gains tax on stock profits.
But Mr Obama claimed that Mr McCain's support for extending Mr Bush's tax cuts would allow $2 trillion in corporate tax breaks, including $1.2 billion for Exxon Mobil Corp, which had earnings last year of $40.61 billion.
"If John McCain's policies were implemented, they would add $5.7 trillion to the national debt over the next decade. That isn't fiscal conservatism, that's what George Bush has done over the last eight years," the Illinois senator said.