The US Treasury Department said it blacklisted Mr Bassil, 50 who is leader of Lebanon’s largest Christian block the Free Patriotic Movement (FPM), because it believes while he held several high-level governments posts he strengthened his base by appointing friends, purchased influence and likely misappropriated state assets.
“The systemic corruption in Lebanon’s political system exemplified by Mr Bassil has helped to erode the foundation of an effective government that serves the Lebanese people,” Treasury Secretary Steven Mnuchin said in a statement.
Mr Bassil responded on social media saying the designation “did not scare him”.
“Sanctions have not scared me nor promises tempted me,” he wrote on Twitter. “I do not turn against any Lebanese… and I do not save myself to let Lebanon perish.”
Mr Bassil’s party has a political alliance with Lebanon’s Iranian-backed Shi’ite movement Hezbollah, which the United States has designated as a terrorist group. The US has sanctioned several Hezbollah members and other politicians linked to the group.
A senior US official separately said Bassil’s support for Hezbollah is “every bit of the motivation” for Friday’s decision.
Mr Bassil has defended the heavily armed group as vital to the defence of Lebanon, which has been crippled by an unprecedented financial collapse. Since last year food prices have more than doubled while the currency has lost 80 per cent of its value.
However, the decision to push ahead with the sanctions may upset attempts by new prime minister designate Saad Hariri to form Lebanon’s new government and break a disastrous political deadlock.
The entire cabinet resigned in the chaotic aftermath of the devastating 4 August blast which killed over 220 people and destroyed swathes of Beirut.
Mr Bassil, who is married to one of the president’s three daughters, became head of the FPM in 2015.It has defined itself as a party defending Christian rights.
Mr al-Hariri, who last month was named prime minister for a fourth time, has described Mr Bassil as a “shadow” president, a comment reflecting the widely held belief that he exercises substantial sway over President Aoun, 87, who became head of state in 2016.
Mr Bassil has served as minister of telecoms, minister of energy and water and minister of foreign affairs.