As US President Donald Trump prepared to head to Saudi Arabia on Friday, Washington and Riyadh issued their first "joint terrorist designation" -- blacklisting a Hezbollah leader.
Hashem Safieddine is head of the executive council of Hezbollah, an Iranian-backed Lebanese armed movement which Washington has branded a "foreign terrorist organization."
"The Kingdom of Saudi Arabia joined the United States in designating Hashem Safieddine," the State Department said in a statement.
"As a result, any of his assets held in Saudi Arabia are frozen, and transfers through the Kingdom's financial sector, are prohibited."
Separately, the department's Bureau of Counterterrorism tweeted that this marked the "first-ever" State Department and foreign nation "joint terrorist designation", underlining the close cooperation between US and Saudi officials.
"The action against Safieddine is the latest example of the strong partnership between the United States and Saudi Arabia in combatting the financing of terrorism," the State Department said.
The official Saudi news agency SPA confirmed Safieddine's listing, and alleged he had given his organization advice on carrying out terrorist acts and on supplying support to Syrian President Bashar al-Assad's regime.
Trump has chosen the kingdom as the venue of his first foreign presidential visit, and this weekend he will meet King Salman and address an audience of up to 50 leaders from across the Muslim world on the threat of extremism.
Safieddine, a Lebanese citizen who is in his 50s, is the head of Hezbollah's executive council, which runs the group's political affairs and social and economic programs in Lebanon's Shiite community.
He is a cousin of Hezbollah's overall leader Hassan Nasrallah, and is spoken of a potential candidate to succeed him and take charge of perhaps the most powerful non-state movement in an unstable region.
The US designation order did not link him to any recent Hezbollah attacks, but noted the group's historical involvement in the 1983 bombing of a US Marines barracks in Beirut, a US embassy bombing in 1984 and a passenger jet hijacking in 1985.
In the same statement, the State Department also added Muhammad al-Isawi -- whom it said had taken over the leadership of the Islamic State (IS) militant group’s franchise in Egypt's Sinai peninsula in August 2016 -- to the sanctions list.
As "specially designated global terrorists," Safieddine and al-Isawi will see any assets they hold in areas under US jurisdiction frozen, and US citizens will be forbidden from any dealings with them.
Separately but simultaneously, the US Treasury added two Yemeni tribal leaders, Hashim Muhsin Aydarus al-Hamid and Khalid Ali Mabkhut al-Aradah, to its own sanctions list, branding them leaders of Al-Qaeda in the Arabian Peninsula.