The U.S. and Israel have launched the allies' most important joint military exercise to date, involving thousands of troops, a dozen ships and 142 aircraft, including bombers with nuclear warheads, Reuters reports.

The Juniper Oak exercise, which runs through Friday, is designed to demonstrate and deepen integration between the U.S. and Israeli armed forces, a senior U.S. Defense Department official said. They come at a time of growing tensions over Iran's nuclear program.

While the drills are likely to draw interest from Tehran, the U.S. official said the exercise will not include mock Iranian targets and is not aimed at any particular adversary.

The exercise includes live-fire exercises and will involve 6,400 U.S. troops, many of whom will be aboard the U.S. aircraft carrier George H.W. About 450 troops are stationed in Israel, the official said.

In addition to the B-52 bombers, F-35, F-15, F-16 and F-18 fighters will be involved. According to the official, the exercise will take place over long distances, including land, sea, air and space.

A senior U.S. official said America's commitment to Israel's security is unshakeable.