President Obama has granted a waiver allowing four countries to continue receiving U.S. military aid even though they use child soldiers, officials said Wednesday.

Human rights groups reacted with surprise and concern, saying the decision would send the wrong message.

"What the president has done is basically given everybody a pass for using child soldiers," said Jo Becker, children's rights director at Human Rights Watch.

Administration officials said cutting off aid would cause more damage than good in countries where the U.S. military is trying to fight terrorism and reform abusive armies.

Obama sent a memo to Secretary of State Hillary Rodham Clinton, dated Monday, saying that it was "in the national interest" to waive a cutoff of military assistance for Chad, the Democratic Republic of Congo, Sudan and Yemen.

Those countries would have been penalized under the Child Soldiers Prevention Act, which was signed into law by President George W. Bush shortly before he left office. The law took effect this year, after the State Department identified six countries that used government soldiers - including Somalia and Burma.

Senior U.S. officials said Wednesday that Yemen was exempted because ending military aid would jeopardize the country's ability to fight al-Qaeda. In Sudan, U.S. military assistance will be critical in helping the unstable southern part of the country build military institutions if it votes to secede in a January referendum, as expected, officials said.

Congo was exempted because U.S.-funded programs there are aimed at helping the military become more professional and less abusive, officials said. Chad got a pass because of its role in fighting terrorism and assistance with the humanitarian crisis in the Darfur region of Sudan. In addition, U.S. aid goes toward helping that country's military end its practice of using child soldiers, officials said.

The exemptions were first reported by the Cable, a blog at ForeignPolicy.com.

One senior official said the countries were not getting off scot-free.

"We put all these countries on notice by naming them as having child soldiers, and making them automatically subject to sanctions," the official said, speaking on condition of anonymity. "Our view was to work with them over the next year to try to solve the problem - or at least make significant progress on the problem - and reassess next year."

Jesse Eaves, policy adviser on children's issues for the humanitarian group World Vision, noted that the law did not mandate a cutoff of all forms of military assistance for offenders. For example, they could have still gotten help in eliminating their use of child soldiers.

"That kind of assistance is still allowed under the law without invoking the waiver. That's why this is a disturbing step," he said.