A statement released by the US read "[Biden and Netanyahu] agreed to remain in close contact over the coming days," however it did not indicate Biden knew the exact plans of a retaliatory attack or had agreed on it. The president and his administration have been reportedly frustrated by Israel's surprise attacks against Hamas and its allies and specifically want Israel to avoid hitting Tehran's oil facilities and nuclear sites.
The statement from the White House regarding the call read: "The President affirmed his ironclad commitment to Israel’s security. He condemned unequivocally Iran’s ballistic missile attack against Israel on October 1st. On Lebanon, the President emphasized the need for a diplomatic arrangement to safely return both Lebanese and Israeli civilians to their homes on both sides of the Blue Line. The President affirmed Israel’s right to protect its citizens from Hezbollah, which has fired thousands of missiles and rockets into Israel over the past year alone, while emphasizing the need to minimize harm to civilians, in particular in the densely populated areas of Beirut. On Gaza, the leaders discussed the urgent need to renew diplomacy to release the hostages held by Hamas. The President also discussed the humanitarian situation in Gaza and the imperative to restore access to the north, including by reinvigorating the corridor from Jordan immediately."
US officials were reportedly hoping for more clarity about Israel's planned retaliation after a meeting between Israeli Defense Minister Yoav Gallant and Defense Secretary Lloyd Austin was supposed to take place at the Pentagon. However Gallant postponed his trip to the US after Netanyahu ordered him to remain in Israel to continue planning the Iran operation.
US officials have said they don't know what the retaliatory attack on Iran will specifically target or when it will take place.