Appearing on ABC's "This Week With George Stephanopoulos," the Democratic presidential contender said if she is elected in November, she will immediately order an investigation into the industry.

"We know that there's market manipulation going on. So I would launch an investigation if I were president right now by the Department of Justice and the Federal Trade Commission," Clinton said.

The New York senator said any attempts to lower gas prices should require the participation of the Organization of Petroleum Exporting Countries.

"I would begin to go directly at OPEC," she said. "I think it's been 25 years where we've, you know, largely just been at the mercy of the OPEC countries."

Clinton said in addition to taking on OPEC members, she would confront oil companies about the rising cost of gasoline.

"You see, I really believe we've got to start right now demonstrating a willingness to take on these oil companies," she said in response to a "This Week" audience question.