The US Justice Department plans to disclose the name of the Saudi official who allegedly helped the hijackers who carried out the 9/11 terror attacks 18 years ago, amid pressure from victims' families and strained relations between Washington and Riyadh.

The decision, first reported by the Wall Street Journal, was announced on Thursday, and follows after a months-long campaign on behalf of victims' families to pressure Donald Trump to make the name public, including a recent letter to the president that said the name would help them to "finally learn the full truth and obtain justice from Saudi Arabia."

The FBI said that the name would be released due to the "exceptional nature of the case", and that just one Saudi name that is most wanted by officials would be released. No other information sought by the families will be released by the FBI.

In the past 18 years, Riyadh has denied any involvement in the attacks, which killed nearly 3,000 people in the World Trade Center, the Pentagon, and in a field in Pennsylvania where passengers managed to down one of the hijacked planes before it could crash into a third target.

For the past few months, the families have sought the disclosure of a four-page FBI summary from 2012, in which three people who may have assisted two of the hijackers are named. Those people allegedly helped two of the hijackers in California to obtain driver's licenses, to find housing, and with other matters.

Unseen 9/11 pictures show Ground Zero in wake of attacks Show all 30 1 /30 Unseen 9/11 pictures show Ground Zero in wake of attacks Unseen 9/11 pictures show Ground Zero in wake of attacks Thousands of photographs taken at Ground Zero in the wake of the 9/11 attacks have come to light after they were purchased at an estate auction. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks The photographs were shot among the rubble of the World Trade Centre towers during the clean-up operation between September and October 2001. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Unseen by the public since 2001, the pictures have emerged as they were bought by an archivist couple at the auction of a private estate. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks “My significant other acquired them at an estate sale as we collect & archive vintage media for public benefit,” says Dr Johnathan Burgess. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks The 2389 pictures were held on five CDs which Dr Burgess passed along to fellow archivist Jason Scott, who uploaded them to his Flickr page. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks The photographer behind the pictures is unknown but Dr Burgess and Scott are working to identify them. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks The Winter Garden Atrium is seen covered in debris. The building is nearby to the site of the former World Trade Centre buildings and was badly damaged when they collapsed. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks The steel frames of a World Trade Centre tower are seen following the attack that led to the building's collapse. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks The steel frames of a World Trade Centre tower are sprayed with water as part of the clean-up operation following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks The steel frames of a World Trade Centre tower are seen following the attack that led to the building's collapse. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks The Winter Garden Atrium is seen covered in debris. The building is nearby to the site of the former World Trade Centre buildings and was badly damaged when they collapsed. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to demolish the remaining sections of building left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks The Winter Garden Atrium is seen covered in debris. The building is nearby to the site of the former World Trade Centre buildings and was badly damaged when they collapsed. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Clouds of dust rise as contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks A tribute message is hung above a US flag on the AmEx tower which was damaged in the collapse of the nearby World Trade Centre towers following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors take a break during the clean-up operation following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Dust rises as contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott Unseen 9/11 pictures show Ground Zero in wake of attacks Contractors work to clear the debris left after the World Trade Centre towers collapsed following the 9/11 attacks. Jason Scott

Two of those people, Fahad al-Thumairy and Omar al-Bayoumi, had previously been named. They both have links to the Saudi government, according to FBI and congressional documentation.

Lawyers for the families had initially attempted to subpoena an un-redacted version of the four-page summary last year.

Others involved in the lobbying effort include allies of Mr Trump's, including congressman Matt Gaetz, who reportedly urged the disclosures after the murder of Washington Post journalist Jamal Khashoggi last year. The Saudi government has been implicated in Khashoggi's murder, in Turkey.

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In spite of that murder, and the growing unease from lawmakers on Capitol Hill who are outraged over Saudi Arabia's involvement in the bloody war in Yemen, Mr Trump has mostly attempted to maintain strong ties with Riyadh.