The US has levied sanctions against people and businesses in Sierra Leone, Ghana and Lebanon over their alleged links to Hezbollah.
The six individuals and seven businesses affected are believed to be employed and owned by Adham Tabaja, one of Hezbollah's most senior financiers.
They are now subject to trade bans and asset freezes as part of the first of a series of US sanctions against the Lebanese Islamist militant group.
The Trump administration feels former President Barack Obama was too soft on Hezbollah, because he didn't want to worsen relations with Iran, which supports the group.
Today will be a "very bad day for" Mr Tabaja, a senior administration official told the news agency AFP, speaking anonymously.
The financier is thought to operate across the Middle East and Africa, raising funds for Hezbollah.