The measures, which could freeze those officials' assets and ban them from doing business in the United States, would likely come in the form of an executive order signed by Barack Obama, the US president, the official said.
But a final decision has yet to be made on the exact timing of such a move and there was no immediate word on whether Assad might be among those targeted for sanctions.
Sanctions would mark an escalation of the US response to Assad's efforts to crush a month-long uprising against his autocratic 11-year rule.
Obama's response so far has been limited to tough words but little concrete action against the Syrian government, in contrast to Washington's role in a NATO-led air campaign against Libyan leader Muammar Gaddafi.
Washington is mindful of its limited ability to influence Damascus, which is closely allied with US foe Iran, and has had chilly relations with the United States.
It is cautious about further military entanglement in the Muslim world where it is already involved in long wars in Iraq and Afghanistan.
Obama, in a statement on Friday, told Syria that its bloody crackdown on protesters "must come to an end now" and accused Damascus of seeking Iranian help to repress its people.
"The brutal violence used by the government of Syria against its people is completely deplorable," Tommy Vietor, White House spokesman, said on Monday.
UN condemnation planned
Meanwhile, four European nations are urging the UN Security Council to strongly condemn the violence against peaceful demonstrators in Syria.
A council diplomat said France, Britain, Germany and Portugal circulated a draft media statement to the other council members.
It will be discussed at a council meeting on Tuesday afternoon, the diplomat said, speaking on condition of anonymity because the consultations have been private.
The draft statement supports secretary-general Ban Ki-moon's call for an independent and transparent investigation into the killings in Syria, where more than 300 people have died in five weeks of unrest, the diplomat said.