May 5: The U.S. says it is sending the USS Abraham Lincoln carrier group and a bomber task force to the Middle East because of a 'credible threat' from Iran.
Since then Washington has announced the dispatch to the region of an amphibious assault ship, a Patriot missile battery and an extra 1,500 troops.
May 8: Iran vows to enrich its uranium stockpile closer to weapons-grade levels starting July 7 if world powers fail to negotiate new terms for its nuclear deal.
The U.S. responds by imposing fresh sanctions on Iran's steel and mining sectors.
Smoke pours from the Norwegian-owned oil tanker on Thursday after it was hit by an explosion near the UAE and Iran in an apparent attack which has put the Middle East on high alert
May 12: Two Saudi oil tankers and two other ships are damaged in mysterious 'sabotage attacks' off the coast of Fujairah, part of the United Arab Emirates.
Washington believes Iran is to blame for the attacks, but Tehran denies involvement.
May 14: Yemen's pro-Iranian Huthi rebels carry out drone attacks near Riyadh, shutting down a key Saudi oil pipeline.
Two days later Saudi-led coalition air strikes hit the rebel-held Yemeni capital Sanaa.
The next day the U.S. orders all non-emergency
