President Barack Obama hit back on Thursday at election-year Republican criticism of his energy policies, offering a staunch defense of his attempts to wean Americans off foreign oil and saying there is no "silver bullet" for high gasoline prices.

Obama sought to deflect growing Republican attacks over rising prices at the pump, blaming recent increases on a mix of factors beyond his control, including tensions with Iran, hot demand from China, India and other emerging economies, and Wall Street speculators taking advantage of the uncertainty.

U.S. gasoline prices have jumped nearly 9 cents in the past week to an average of $3.61 a gallon, and are expected to rise further toward the crucial $4 mark through the summer driving season and the approach of the Nov. 6 election.

In a visit to the University of Miami less than nine months before the presidential election in which he will seek a second term, Obama offered a modest series of proposals aimed at diversifying fuel supplies and increasing energy efficiency.

"It's the easiest thing in the world (to) make phony election-year promises about lower gas prices," Obama said, offering his most comprehensive rebuttal yet of the intensifying Republican criticism.

"What's harder is to make a serious, sustained commitment to tackle a problem that may not be solved in one year or one term or even one decade," he said.

Obama's speech was part of a broader White House strategy to try to regain the upper hand in the debate and deflect blame, but the president's arguments may fall on deaf ears if gas prices continue to rise and cause financial pain for voters.

Republicans have made rising gas prices one of their main attack lines against Obama, sensing an electoral vulnerability for the president. His re-election prospects depend in part on his ability to keep a fragile economic recovery afloat and to continue reducing high unemployment.

Republicans seeking to dislodge Obama from the White House are seeking to pin the higher prices on the president's tax and environmental policies they say have hindered domestic production and kept the United States at the mercy of imports.

They cite his decision to block the Keystone pipeline that would transport Canadian oil to refineries in Texas as proof he is beholden to environmentalists .

The Obama administration has delayed a final decision on Keystone until after the election, saying the proposed route could pose a danger to water supply in the nation's breadbasket.

Obama needs to win the war of words to gain an upper hand over Republicans in Western battleground states including Colorado, Nevada and New Mexico, where people drive a lot and feel the sting of rising prices acutely.

Gasoline prices have climbed alongside crude futures, the major component in determining the price of gasoline, due to concerns about a potential disruption of supplies from Iran, which is locked in a standoff with the West overTehran's disputed nuclear program.

U.S. crude prices have jumped 9 percent this year, nearing $108 a barrel on Thursday, the highest level since May, 2011.

DRILL, DRILL, DRILL

As gasoline prices become an increasingly important election issue, Republicans are scrambling to prove they can offer relief. On Wednesday, Republican candidate Newt Gingrich, the former speaker of the House of Representatives, promised gasoline prices of $2.50 a gallon if he won the White House.

"You can bet that since it's an election year, they're already dusting off their three-point plans for $2 gas," Obama said. "I'll save you the suspense: Step one is drill, step two is drill and step three is keep drilling."

While Obama said he had asked officials to look for opportunities to help consumers in the short term - in areas such as permitting and delivery bottlenecks - he repeated there would be no "silver bullet" for America's energy crunch, and said real change would come only in the long run.

The trio of proposals announced in Miami included a $30 million competition in natural gas technologies and a $14 million program to development algae-based fuel.

Obama highlighted steps already taken to expand domestic production and improve fuel efficiency.

He also repeated calls to roll back tax incentives for the oil industry and urged renewal of a clean energy tax credit in Congress, where lawmakers are deeply divided and little legislative action is expected this year.

His remarks were met with disdain from top Republicans.

"Facing an election, the President would like everyone to forget that gas prices have doubled over the past three years while he consistently blocked and slowed the production of American-made energy," said Brendan Buck, a spokesman for John Boehner, the Republican speaker of the House of Representatives.

While Republicans blame high oil prices on actions such as Obama's Keystone pipeline decision, an oil boom led by North Dakota is expected to push U.S. crude output this year to its highest level since 1999.

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Lawmakers from Obama's own party are asking him to take steps to ease the price pressure in the short term. Democratic lawmakers on Wednesday urged the White House to signal it is ready to tap the country's strategic petroleum reserve, which contains about 696 million barrels of oil.

Obama made no mention of taking that step in his speech.