In 2009, the deputy chief of mission of the U.S. embassy in Baku, Donald Lu, sent a cable to the State Department’s headquarters in Foggy Bottom titled “Azerbaijan’s discreet symbiosis with Israel.” The memo, later released by WikiLeaks, quotes Azerbaijan’s President Ilham Aliyev as describing his country’s relationship with the Jewish state as an iceberg: “nine-tenths of it is below the surface.”

Why does it matter? Because Azerbaijan is strategically located on Iran’s northern border and, according to several high-level sources I’ve spoken with inside the U.S. government, Obama administration officials now believe that the “submerged” aspect of the Israeli-Azerbaijani alliance — the security cooperation between the two countries — is heightening the risks of an Israeli strike on Iran.

In particular, four senior diplomats and military intelligence officers say that the United States has concluded that Israel has recently been granted access to airbases on Iran’s northern border. To do what, exactly, is not clear. “The Israelis have bought an airfield,” a senior administration official told me in early February, “and the airfield is called Azerbaijan.”