(Adds Obama interview with NPR)

WASHINGTON, Dec 15 (Reuters) - Russian President Vladimir Putin supervised his intelligence agencies' hacking of the U.S. presidential election and turned it from a general attempt to discredit American democracy to an effort to help Donald Trump, three U.S. officials said on Thursday.

U.S. intelligence agencies' conclusion that Russia tried to influence the election by hacking people and institutions, including Democratic Party bodies, has angered President-elect Trump, who says he won the Nov. 8 vote fairly. Russian officials have denied accusations of interference in the U.S. election.

Separately, a senior White House official said on Thursday that Putin was likely to have been aware of the cyber attacks but he fell short of accusing the Russian president.

"I don't think things happen in the Russian government of this consequence without Vladimir Putin knowing about it," Ben Rhodes, the White House's deputy national security adviser, told MSNBC. "When you're talking about a significant cyber intrusion like this, we're talking about the highest levels of government."

The U.S. officials - who have knowledge of intelligence information on the matter - said on the condition of anonymity that the hacking of U.S. political groups and figures had a more general focus at first.

"This began merely as an effort to show that American democracy is no more credible than Putin's version is," one of the officials said.

"It gradually evolved from that to publicizing (Hillary) Clinton's shortcomings and ignoring the products of hacking Republican institutions, which the Russians also did," the official said.

By the fall, the official said, it became an effort to help Trump's campaign because "Putin believed he would be much friendlier to Russia, especially on the matter of economic sanctions" than Democratic rival Clinton.

Democratic President Barack Obama said in an interview with National Public Radio that the United States will take action against Russia.

"I think there is no doubt that when any foreign government tries to impact the integrity of our elections ... we need to take action and we will," he said according to excerpts of the Thursday interview released by NPR.

"At a time and a place of our own choosing. Some of it may be ... explicit and publicized; some of it may not be. ... Mr. Putin is well aware of my feelings about this, because I spoke to him directly about it," Obama said.

NBC reported earlier that U.S. intelligence officials have "a high level of confidence" Putin was personally involved in the Russian cyber campaign against the United States.