US Democratic presidential candidate Barack Obama dropped a plan to visit wounded American troops in Germany on Friday amid concerns the stop would be viewed as a political event.
The Pentagon said arrangements had been put in place for Mr Obama to visit Landstuhl Regional Medical Center as a US senator, without his campaign staff, as political activity is forbidden on US military facilities.
But an Obama adviser said the candidate was concerned the trip would have been viewed as a campaign event.
"Senator Obama did not want to have a trip to see our wounded warriors perceived as a campaign event when his visit was to show his appreciation for our troops, and decided instead not to go," said retired Maj. Gen. Scott Gration, who advises Obama on national security matters.
He said the Pentagon told Mr Obama's campaign that the military would consider the visit a campaign event.
But the Pentagon insisted it had been ready to welcome Obama at the hospital, without his campaign staff or accompanying reporters.
"We advised that Senator Obama would be welcome to visit Landstuhl or any other military hospital in his capacity as a US senator, but his campaign staff would not," Pentagon press secretary Geoff Morrell said.
Mr Obama recently visited Walter Reed Army Medical Center, the flagship military hospital in Washington, on that basis, Morrell said.
"For whatever reason, they made a determination that they did not want to proceed with the visit," Morrell said. "We were ready, willing and able to host them at Landstuhl."
The Landstuhl medical center near the city of Kaiserslautern is the largest American hospital outside the United States.
Senior Obama aide Robert Gibbs noted the senator had visited troops during the earlier part of his foreign tour in Iraq and Afghanistan, including a stop at a combat support hospital in the secure Green Zone in Baghdad.
Mr Obama undertook the first part of his tour as a member of a delegation of US senators, while the follow-on trip to Europe is in his capacity as a presidential candidate.
On Thursday, about 200,000 people admirers cheered Mr Obama during a speech in Berlin's Tiergarten park, welcoming his call for unity with Europe, and admission that America had made mistakes.
