U.S. President Barack Obama ordered his government Thursday to quickly approve construction of a segment of a controversial oil pipeline, but warned the country's motorists that global tensions are likely to keep gasoline prices high.

Speaking at an industrial site in the oil hub of Cushing, Oklahoma, Mr. Obama said he had directed government agencies to expedite approval of a 780-kilometer pipeline from there to refineries on the coast of the Gulf of Mexico. But he put off a final decision on a longer pipeline that Calgary-based TransCanada wants to build from its oil fields in Alberta, Canada to the Oklahoma connection.

“And today we're making this new pipeline from Cushing to the gulf a priority. So the southern leg of it, we'll make it a priority and we're going to go ahead and get that done. The northern portion of it, we're going to have to review properly to make sure that the health and safety of the American people are protected. That's common sense.”

With gas prices in the U.S. topping more than $1 a liter , Republican candidates seeking to oust Mr. Obama, a Democrat, in November's national election have heightened their attacks on his energy policies. They have criticized his decision earlier this year to reject to full construction of what is known as the Keystone XL pipeline. His leading Republican foe, one-time venture capitalist Mitt Romney, has called for Mr. Obama to fire his three top energy advisers.

But the president staunchly defended his energy policies in Oklahoma, a central state whose voters overwhelmingly rejected his candidacy four years ago. He said the United States is “drilling all over the place” and would continue to tap new reserves.

“And as long as I'm president, we're going to keep on encouraging oil development and infrastructure and we're going to do it in a way that protects the health and safety of the American people. We don't have to choose between one or the other, we can do both.”

Mr. Obama said the United States must continue to develop more clean-energy sources as well as expand oil drilling. He blamed the recent increase in gas prices — the highest ever in the U.S. for this time of year — on tensions over the West's attempt to get oil-producing Iran to curtail its nuclear development program.

“And that's not the future that we want. We don't want to be vulnerable to something that's happening on the other side of the world somehow affecting our economy, or hurting a lot of folks who have to drive to work.”