Iran's unprecedented strikes on a US base in Qatar were carefully calculated to provide an exit from hostilities with Washington and set up a truce with Israel, according to analysts and an official.Monday's missile launches were signalled well in advance,

In public, Qatar was insisting on the right to defend itself after Iran attacked a U.S. military site in the emirate. Behind the scenes, it was already mediating a truce between Israel and Iran.

The Pentagon already had begun taking measures to strengthen its firepower in the Middle East and protect U.S. bases there.