Williams in a statement stressed that inclusive political dialogue was the best way to preserve the peace in Lebanon.
"As events in the Arab world have shown, dialogue among all sides in the country is the only way to resolve differences but also to move forward with any country's political, social and economic needs," he said.
The previous government led by caretaker Prime Minister Saad Hariri collapsed Jan. 11 after Hezbollah led its opposition allies in mass resignations. Hezbollah was upset by the previous government's support for a tribunal probing the 2005 assassination of former Lebanese Prime Minister Rafik Hariri, Saad Hariri's father.
The tribunal released a sealed indictment in January. Hezbollah is widely expected to be named by the tribunal, though the Shiite resistance movement claims to have evidence linking Israel to the Hariri plot.
Williams in his statement reminded Mikati that any government in Beirut must remain committed to its international obligations.
Mikati, a one-time ally of Saad Hariri, hasn't been able to form a new government because of spats between rival political factions.