Defence Secretary Patrick Shanahan says the potential of attacks by Iran has been “put on hold” by US counter-measures.
The U.S. has warned of a threat from Iran in recent weeks and Mr Shanahan briefed lawmakers at a closed-door meeting.
Tension has risen sharply, with the U.S. deploying military assets to the Gulf to tackle the unspecified threats.
U.S. president Donald Trump has maintained a strong anti-Iran policy since taking office and last year unilaterally withdrew the U.S. from a nuclear deal with Iran and five world powers.