From US military deployments to alleged "threats" from Iran and attacks on oil tankers and installations, here is a timeline of escalating tensions in the Gulf:
- 'Credible threat' -
On May 5, the United States says it is sending the USS Abraham Lincoln carrier group and a bomber task force to the Middle East.
The deployment is "in response to a number of troubling and escalatory indications and warnings" related to Iran, acting defence secretary Patrick Shanahan says a day later.
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.
- Sanctions against Iran -
On May 8, Iran says it is preparing to increase enriched uranium and heavy water production as part of its decision to stop certain commitments made under the 2015 nuclear deal with world powers.
A year after Washington unilaterally withdrew from the deal and later reimposed sanctions on Tehran, US President Donald Trump announces new measures against Iran's steel and mining sectors.
In June, Washington hits Iran's petrochemical group PGPIC -- the country's largest and most profitable such group, with sanctions.
- 'Sabotage' -
On 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.
Fujairah is the only Emirati terminal located on the Arabian Sea, bypassing the Strait of Hormuz through which most Gulf oil exports pass.
Iran, which has repeatedly threatened to close the strait in case of a military confrontation with the United States, calls the incidents "alarming and regrettable".
- Drone attacks near Riyadh -
On 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.
On May 15, the US orders all non-emergency diplomats to leave Iraq, due to an "imminent" threat from Iranian-linked Iraqi militias.
- War of words -
Trump warns on May 19 that if Iran attacks American interests "that will be the official end of Iran".
Iranian Foreign Minister Mohammad Javad Zarif says the "genocidal taunts" of US Trump will not "end Iran".
On May 27 Trump says the US is "not looking for regime change" in Iran.
- Arab support for Riyadh -
On May 30, Saudi Arabia -- which accuses Iran of being behind the acts of sabotage and the drone attack in May -- gets the backing of Arab leaders in its standoff with Tehran at summits organised by Riyadh.
Iran accuses Riyadh of "sowing division".
On June 6, the UAE says a multinational investigation into the sabotage attacks point to the likelihood a state was behind them, without incriminating Iran.
- Shinzo Abe in Tehran -
On June 12, Japanese Prime Minister Shinzo Abe arrives in Tehran in a bid to mediate between Washington and Tehran.
A day later he meets Iran's supreme leader Ayatollah Ali Khamenei who tells him: "I don't consider Trump as a person worthy of exchanging messages with. I have no response for him and will not answer him."
A Yemeni rebel missile attack on an airport at Abha, in southwestern Saudi Arabia, wounds 26 civilians of different nationalities on June 12.
- New shipping incident -
On June 13, two tankers, Norwegian and Japanese, come under "attack" in the Gulf of Oman, according to the Norwegian maritime authority and the Japanese shipowner.
The US Fifth Fleet says that it received two separate distress calls from the tankers in a "reported attack".
Iran speaks initially of "accidents" and says it rescued 44 crew.
Foreign Minister Zarif says the tanker "attacks" as Abe visits are "suspicious".