A key clause in a U.S. military agreement creating a no-fly zone over Iraq is set to run out at the end of the year. The clause, inserted in the agreement following Iranian pressure on Iraq's Shi'ite prime minister, Nouri al-Maliki, was apparently a way to thwart an Israeli air attack on Iran.

The agreement between the United States and Iraq, signed in November 2008, is due to run out at the end of this year when U.S. forces withdraw from Iraq under the timetable set by President Barack Obama (although thousands of advisers will remain ).

Clause 27 of the agreement states that, if asked, the United States must thwart threats to Iraq's sovereignty and not let its land, territorial waters or airspace be used for attacks on other countries.

The clause has special significance considering the increased speculation in recent days that Israel might attack Iran's nuclear sites. It is unclear to what extent the United States will be obligated under the clause after its forces leave Iraq. In any case, the obligation will certainly not be as binding as it is now.

The shortest air route from Israel to Iran is over Iraq.

In September 2007, when, according to foreign sources, the Israel Air Force attacked nuclear sites in northern Syria, the planes reportedly jettisoned detachable fuel tanks over Turkey on their way back.

The reports embarrassed Ankara, which asked Israel for clarifications.

Considering the current troubled relations between Israel and Turkey, it is very doubtful that in an attack on Iran, Israel could use Turkish air space.