WASHINGTON -- President Obama pledged Monday that the United States "will stand with the people of Japan" in the difficult days ahead.

Making remarks at the top of a speech on reforming "No Child Left Behind," the president said he is "heartbroken by the images of devastation in Japan."

Calling the people of Japan "some of our closest friends and allies," the president said he knew everyone has been watching "the full magnitude of this tragedy unfold." Ohama said the U.S. will offer any assistance it can as Japan continues to recover from a massive earthquake, tsunami and nuclear energy plant meltdown.

Meanwhile, U.S. efforts have been hampered by the Navy having to move several U.S. ships away from the troubled Japanese nuclear plant after low-level radiation was detected on 17 helicopter crew members positioned there for relief efforts.

Navy Cmdr. Jeff Davis, a spokesman for the U.S. 7th Fleet, said Monday that the Navy is committed to continuing the operation to help the Japanese after last week's earthquake and tsunami. But officials had to figure out how to continue safely after airborne radiation was detected Sunday by the carrier USS Ronald Reagan and on a helicopter crew returning to the ship from search and rescue operations.

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By moving the ships in the carrier group out of the downwind path of the power plant, Davis says the navy can continue with less risk to Americans participating.

The Associated Press contributed to this report.