Aug 14 (Reuters) – The U.S. military on Wednesday said Iranian forces briefly boarded a Liberian-flagged oil near the Strait of Hormuz, heightening tensions in the world’s busiest oil waterway.

Sources said the Iranian action was retaliation against the Greek owner of some of the vessels that were carrying fuel to Venezuela.

The cargoes are covered by a U.S. warrant for seizure and the tankers are sailing to the United States.

Hormuz has been the site of many confrontations between regional and international powers over the last decades.

Below are details about the Strait:

WHAT IS THE STRAIT OF HORMUZ?

* The strait lies between Oman and Iran

* It links the Persian Gulf with the Gulf of Oman to the south and the Arabian Sea beyond

* It is 21 miles (33 km) wide at its narrowest point, with the shipping lane just two miles (3 km) wide in either direction

* The UAE and Saudi Arabia have sought to find other routes to bypass the Strait, including building pipelines

WHY DOES IT MATTER?

* In 2018, 21 million barrels per day (bpd) of oil flowed through it, or the equivalent of about 21% of global petroleum liquids demand at the time, the U.S. Energy Information Administration says.

* OPEC members Saudi Arabia, Iran, the UAE, Kuwait and Iraq export most of their crude via the Strait

* Qatar, the world’s biggest liquefied natural gas (LNG) exporter, sends almost all its LNG through the Strait

POLITICAL TENSIONS

* The United States has imposed sanctions on Iran aimed at halting its oil exports

* Iran has threatened to disrupt oil shipments through the Strait of Hormuz if the United States tries to strangle its economy

* The U.S. Fifth Fleet, based in Bahrain, is tasked with protecting commercial shipping in the region MAJOR PAST INCIDENTS

* 1980-1988 – During the Iran-Iraq war, the two sides sought to disrupt each other’s oil exports in what is known as the Tanker War

* July 1988 – U.S. warship Vincennes shoots down an Iranian airliner, killing all 290 aboard, in what Washington says was an accident and Tehran says was a deliberate attack

* Early 2008 – The United States says Iranian vessels threaten three U.S. Navy ships in the Strait

* July 2010 – Japanese oil tanker M Star is attacked in the Strait – a group called Abdullah Azzam Brigades linked to al Qaeda claims responsibility

* January 2012 – Iran threatens to block the Strait in retaliation for U.S. and European sanctions aimed at curbing Tehran’s nuclear programme

* May 2015 – Iranian ships seize a container ship in the Strait and fire shots at a Singapore-flagged tanker that Iran says damaged an oil platform

* July 2018 – President Hassan Rouhani hints Iran could disrupt oil trade through the Strait in response to U.S. calls to reduce Iran‘s oil exports to zero

* May 2019 – Four ships, including two Saudi oil tankers, are attacked in the Persian Gulf just outside the Strait. U.S. officials blame Iran, Tehran denies the charges

* June 2019 – Two tankers are attacked south of the Strait which Washington blames on Iran and Tehran denies

* June 2019 – Iran shoots down a U.S. drone

* July 2019 – The USS Boxer destroys an Iranian drone in the Strait after it threatens the U.S. Navy ship but Iran denies it has lost a drone

* July 2019 – Iran seizes British-operated oil tanker Stena Impero in the Strait

Sources: Reuters/Refinitiv/Energy Information Administration (Reporting by Ahmad Ghaddar; editing by Barbara Lewis)