[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2008/images/07/25/art.obamaplane.gi.jpg caption="Obama canceled a trip to a U.S. military hospital in Germany."](CNN) - A top aide to Barack Obama said Friday the campaign canceled a scheduled visit to an American military base in Germany the day before because the Pentagon expressed concerns it would be viewed as a campaign trip.
The incident is representative of the delicacy with which the Obama campaign has attempted to navigate the Illinois senator's entire journey abroad - at once staging elaborate photo-ops beamed back to the American media while at the same time insisting that Obama's trip is not a political one by definition.
The Illinois senator had planned on visiting a U.S. military hospital in Landstuhl, Germany - currently housing American troops injured in Iraq. The visit was expected to come after Obama's speech in Berlin. But the campaign suddenly announced Thursday the stop had been canceled, saying then Obama had determined it would be "inappropriate."
But speaking to reporters Friday, Senior Obama adviser Robert Gibbs said Ret. Major Gen. Scott Gration, currently a policy adviser to the campaign, received a call from Pentagon officials earlier in the week who expressed concern with the trip - specifically because Obama was heading there on his campaign plane and campaign staff would be accompanying him on the visit.
After speaking with Gration, the campaign decided to cancel the trip. Gibbs said Obama is "comfortable with the decision" because he did not want to make the troops part of a campaign event.
But the decision to cancel the event drew widespread criticisms from conservative blogs and the McCain campaign.
"It is never ‘inappropriate’ to visit our men and women in the military," McCain spokesman Brian Rogers said.
Pentagon spokesman Bryan Whitman told reporters later Friday the Pentagon did not explicitly say Obama should not visit the base, but was concerned with whether his capacity there would be one of a presidential candidate, not a senator.
"We do have certain policy guidelines for political campaigns and elections. And what is appropriate and what is not appropriate in those situations. But the Pentagon certainly did not tell the senator that he could not visit Landstuhl," Whitman said.
"Generally speaking, the military tries very hard not to get involved in political campaigns," he said. "Conducting a campaign speech for example on a military installation is not something that would be appropriate to do."
In another sign the Obama campaign has at times had difficulty maintaining the notion the presidential candidate's trip is devoid of politics, it also received criticism Thursday night for distributing an e-mail to supporters that highlighted Obama's Berlin speech and included a link for online donations.
The campaign insists it was not a fundraising e-mail.