Unnamed senior diplomats and military intelligence officials were interviewed in the Foreign Policy magazine report, "Israel's Secret Staging Ground," published Wednesday.
"The Israelis have bought an airfield … and the airfield is called Azerbaijan," a senior administration official was quoted as saying.
The Azeri military has four abandoned Soviet-era airfields that would potentially be available to Israel and four air bases for their own aircraft, the report says, quoting details from Military Balance 2011 from the International Institute for Strategic Studies in London.
Senior U.S. intelligence officials are increasingly concerned Israeli military expansion in Azerbaijan will hamper efforts to dampen tensions with Iran, an official told Foreign Policy.
"We're watching what Iran does closely … but we're now watching what Israel is doing in Azerbaijan. And we're not happy about it," an intelligence officer said.
Ties between Israel and the predominantly Muslim Azerbaijan are believed to be robust, and even if Israel doesn't use the fields for a direct airstrike on Iran, Azerbaijan could still prove useful for Jerusalem's interests in the region, the report says.
American intelligence and diplomatic officials say they believe access to the air bases by Israel was gained through a series of quiet political and military understandings. A senior retired U.S. diplomat was quoted in the report as saying he doubts "there's actually anything in writing … but I don't think there is any doubt -- if Israeli jets want to land in Azerbaijan after an attack, they'd probably be allowed to do so. Israel is deeply embedded in Azerbaijan, and has been for the last two decades."
The Israeli and Azeri embassies in Washington, the Israeli Army and Mossad all refused to comment on the report.