The U.S. and Israel will begin their largest joint air and missile defense exercise by the end of this month, sending a message of solidarity between the nations to Iran and to American voters just before the Nov. 6 presidential election.

The U.K. and Germany also will participate in the three- week “Austere Challenge” exercise involving as many as 3,500 U.S. personnel in the region along with 1,000 members of the Israel Defense Forces, Navy Lieutenant Commander Wendy Snyder, a Pentagon spokeswoman, said in an e-mailed statement.