President Obama made clear Sunday he has no plans to overrule Attorney General Eric Holder's decision to open an investigation into whether CIA agents under the Bush administration crossed the legal line while interrogating terror suspects. 

Obama gave Holder leeway to investigate even after seven former CIA directors wrote Obama a letter urging him to stop the probe. 

"I appreciate the former CIA directors wanting to look out for an institution that they helped to build. But I continue to believe that nobody is above the law," Obama said on CBS' "Face the Nation." "I want to make sure that as president of the United States that I'm not asserting in some way that my decisions overrule the decisions of prosecutors who are there to uphold the law." 

The former CIA directors, whose tenures span back as far as 35 years, wrote in their letter to the president that the cases have already been investigated by the CIA and career prosecutors, and that to reconsider those decisions makes it difficult for agents to believe they can safely follow legal guidance. 

"Attorney General Holder's decision to re-open the criminal investigation creates an atmosphere of continuous jeopardy for those whose cases the Department of Justice had previously declined to prosecute," they wrote.  

"Those men and women who undertake difficult intelligence assignments in the aftermath of an attack such as September 11 must believe there is permanence in the legal rules that govern their actions," the seven added. 

Obama has tried to keep his distance from the controversial decision to reopen the interrogation cases. He said Sunday, as he has for months, that he prefers to "look forward and not backwards" -- but critics say that if the president really wanted to follow that advice, he could halt the inquiry. 

The president said Sunday that he does not want "witch hunts" and said prosecutor John Durham is not yet pursuing a "criminal investigation." 

"They are simply investigating what took place," Obama said. 

The Washington Post reported over the weekend that the Justice Department's review will center on a narrow portfolio of cases. 

The article also said that Holder did not read key memos before making his decision -- the memos were written by prosecutors under the Bush administration who explained their decision not to pursue charges against the CIA officers.