WASHINGTON (AP) — President Barack Obama's campaign accused Republican Mitt Romney of siding with "Big Oil" in a new television ad released Monday, signaling an escalation of a general election campaign and a vigorous debate over gas prices.

"In all these fights, Mitt Romney's stood with Big Oil — for their tax breaks, attacking higher mileage standards and renewables," the Obama campaign said in the new ad, which marked the first time the president's campaign has publicly attacked Romney by name and made clear it views the former Massachusetts governor as Obama's likely opponent next fall.

Obama's second ad of the presidential campaign came hours after the release of a similar spot by the Democratic outside group Priorities USA Action, which argued that the oil industry is trying to help Romney win the White House to protect its own profits and tax breaks.

The twin ads sought to blunt a $3 million-plus ad campaign launched by the American Energy Alliance blaming Obama for rising gas prices and his decision to delay the Keystone XL pipeline project. It reflected the degree to which Democrats feel vulnerable as gasoline prices top $4 a gallon in many U.S. markets and pose a threat to the economic recovery, the key benchmark in Obama's case for re-election.

Beyond energy, the ads made clear that Obama's campaign had entered a new stage in which it hopes to define Romney as being beholden to big business well before he secures his party's nomination and seeks to present himself as a viable alternative to Obama.

Romney's campaign and Republicans said the ads reeked of desperation from a White House grappling with high gas prices. Romney spokeswoman Andrea Saul said it was no surprise that Obama was "spending his soon-to-be $1 billion war chest to attack Mitt Romney and deflect blame for his failure to control gas prices."

The Republican National Committee, which is gearing up to help the GOP nominee quickly pivot to the general election, said Obama was "panicked" because his energy policies had "failed to do anything about soaring gas prices that are hurting families across the country."

The ads from the outside groups were airing in states expected to play a deciding role in the presidential election: Colorado, Florida, Iowa, Michigan, New Mexico, Nevada, Ohio and Virginia. The Obama campaign ad was appearing in six of those states but not airing in Michigan and New Mexico.

Obama's campaign has sought to shackle Romney to business and oil interests at a time when oil companies rake in soaring profits. It noted that the American Energy Alliance was run by a former lobbyist for Koch Industries, an industrial firm whose top executives are Charles and David Koch, both prominent supporters of conservative causes.

The ads, however, show the degree to which the Obama campaign needs to defend itself against unlimited money raised by outside groups supporting Republicans. Priorities USA has struggled to compete with some of its Republican rivals, forcing Obama's team to go on the defense and spend money on TV ads seven months before the election.

Appearing with the leaders of Canada and Mexico, Obama faced questions Monday at a White House news conference tinged with presidential politics. Obama defended his health care law following last week's Supreme Court arguments on the constitutionality of his signature accomplishment, saying he expected the court to uphold the law.

Asked about Romney's recent questioning of Obama's support for "American exceptionalism," the notion that America plays a unique role as the world's leading superpower, the president said his "entire career has been a testimony to American exceptionalism."

He then offered a sharp retort against Romney, whose quest for the Republican nomination has dragged into the spring against Rick Santorum and Newt Gingrich. "I will cut folks some slack for now because they're still trying to get their nomination," Obama said.

A few hours later, his campaign had disclosed its plans to strike back at Romney on television.