"It is critical that a government committed and able to implement priority reforms be formed now," Secretary of State Antony Blinken said after Hariri abandoned his efforts to form a government nine months after accepting the challenge.
The country is deep in crisis and international donors remain adamant that a government must be established before they can provide funding.
But political squabbling has repeatedly stymied such efforts and sent the currency to unprecedented lows that leave imported medicine and fuel increasingly unaffordable.
"Lebanon's political class has squandered the last nine months," Blinken said in a statement.
"The Lebanese economy is in free-fall and the current government is not providing basic services in a reliable fashion," he added.
"Leaders in Beirut must urgently put aside partisan differences and form a government that serves the Lebanese people."
