The Pentagon on Tuesday defended stricter rules on media relations for the US military, saying the department needed to better manage its contacts with reporters.

The new rules, laid out by Defense Secretary Robert Gates in a July 2 memo, drew criticism from the media rights group Reporters Without Borders (RSF) and concern from journalists at a Pentagon briefing.

Press Secretary Geoff Morrell acknowledged that the Pentagon public affairs office would have the authority to vet and veto some interviews as necessary, but insisted that the rules would not stifle media coverage.

"Hopefully, if we do this right, you will not notice the impact of this memo," Morrell told reporters.

The secretary's guidelines, first reported in the New York Times, came only days after the commander in Afghanistan, General Stanley McChrystal, was forced to step down over a Rolling Stone magazine profile, in which he and his aides made disparaging remarks about administration officials.

Gates' memo states that "prior to interviews or any other means of media and public engagement with possible national or international implications, all component leaders or their public affairs officers must notify" the defense secretary's public affairs section.

Morrell said the new rules had been planned long before the Rolling Stone episode but said the article was an example of "a lack of coordination" that Gates wanted to address.

"He's been concerned, there are too many people, talking to too many people about too many subjects without enough coordination and discipline," he said.

"This is an effort to try to get a better grip on how we as an enormous department communicate with the press corps worldwide," he said.

Reporters Without Borders said in a statement that it is "disturbed by the decision to tighten restrictions on military relations with the media."

"The authorities clearly have a right to protect classified information but these restrictions could complicate journalists? work and make it harder for them to access information," it said.

Gates' memo also warned against leaking classified information as well as "unclassified, but sensitive, pre-decisional, or otherwise restricted information" without permission.

Citing the passage, Reporters Without Borders said the wording "needs to be clarified as it is too vague and lends itself to too wide a range of interpretations."

At a briefing earlier with Colonel Dave Lapan, a Pentagon spokesman, journalists voiced concern that the memo would have a "chilling effect" and could discourage officers in Afghanistan or elsewhere from speaking to the media without explicit approval from Washington.

Lapan played down the effect of the memo, saying it was merely restating current policy and would not have a "chilling effect" on journalistic inquiry.

"It will not change substantially how people deal with the media," he said.

A spokeswoman for RSF, Clothilde Le Coz, disagreed.

"It might not change the way people will deal with the media. But it will change how journalists can get information," she said.