Aljazeera's skybox is one of the several that media organisations use as broadcast booths to cover the upcoming convention in Boston to confirm John Kerry's nomination as George Bush's presidential challenger in November.
"We found that the banner disappeared for some reason," Aljazeera's Washington bureau chief Hafiz al-Mirazi said.
"We contacted the Democratic National Convention and the people who are organising the convention. And then they said it has been removed, maybe for lack of enough space or something like that, although they approved originally the sign and everything on it. And every time we get different answers."
"And finally, they said, 'Sorry, we cannot put it back." And it's the only news organisation sign that was taken," al-Mirazi pointed out.
A convention spokeswoman said Aljazeera was not a special case.
"Our first priority is putting a convention on, not advertising for the media," Peggy Wilhide said.
In place of Aljazeera's logotype will be a banner reading "Strong for America."