U.S. President Barack Obama speaks during a news conference at the White House in Washington D.C. on Aug. 9, 2013. Obama on Friday pledged measures to strengthen oversight and transparency of the National Security Agency (NSA)'s classified surveillance programs following two months of controversies. (Xinhua/Fang Zhe)

U.S. President Barack Obama on Friday pledged measures to strengthen oversight and transparency of the National Security Agency (NSA)'s classified surveillance programs following two months of controversies.

"It's not enough for me as president to have confidence in these programs. The American people need to have confidence in them as well," said Obama at a White House press conference.

He unveiled four measures as part of the efforts to stem the controversies over the surveillance programs, which have been secretly conducted for years and revealed by former NSA contractor Edward Snowden in June.

"But given the scale of this program, I understand the concerns of those who would worry that it could be subject to abuse," said Obama.

The president said that he would work with Congress to pursue " appropriate reforms" to Section 215 of the Patriot Act, which allows the government to collect phone call records.

He will also work with the lawmakers to "improve the public's confidence in the oversight" of the Foreign Intelligence Surveillance Court (FISC), which grants government agencies the warrants to scoop data from individuals and companies.

The president also vowed to make public more information about the surveillance programs, and to form a high-level group of outside experts to review the "entire intelligence and communications technologies."

"We can take steps to put in place greater oversight, greater transparency, and constraints on the use of this authority," he stressed.

Obama's move came ahead of his week-long vacation and after months of fierce controversies over the NSA programs since Snowden 's leak.