FACTBOX-Strait of Hormuz: the world's most important oil artery

Iran's ambassador to Britain warned against escalating tensions on Sunday, a day ahead of an expected response from the UK which could include fresh sanctions on Tehran or other steps after its seizure of a British-flagged oil tanker. Britain has called the capture of the Stena Impero in the Strait of Hormuz on Friday a "hostile act".

Below are details about the Strait: WHAT IS THE STRAIT OF HORMUZ?

* The strait lies between Oman and Iran * It links the 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? * Almost a fifth of the world's oil passes through the Strait - some 17.4 million barrels per day (bpd) versus consumption of about 100 million bpd in 2018, data from analytics firm Vortexa showed

* 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 of its LNG through the Strait POLITICAL TENSIONS

* The United States has imposed sanctions on Iran aimed at halting its oil exports * U.S. waivers which had allowed continued sales of Iranian oil to eight countries - China, Greece, India, Italy, Japan, South Korea, Taiwan and Turkey - expired on May 2

* 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 seek 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 is 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 which 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 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