Syria denied the accusations and Hariri has compared them to the false American charges that Iraq had weapons of mass destruction ahead of the 2003 U.S.-led invasion.
The Iranian-backed Hezbollah has refused to confirm or deny the claims.
Hariri's government, formed in November 2009, is made up of a coalition of Western-backed factions and Syrian-supported groups led by Hezbollah. He has recently reconciled with Syria, which he has blamed for the 2005 assassination of his late father, former prime minister Rafik Hariri.
"Hariri does not want to cut his relations with Washington. His reconciliation with Syria and his stances in which he defended Hezbollah's weapons have caused for him a tacit problem with the Americans," said Ibrahim Bayram of Lebanon's leading An-Nahar newspaper.
"Hariri is trying to balance between his recent relation with Syria and his old relations with the United States," he said.
The U.S. State Department accused Damascus of "provocative behavior" in supplying arms to Hezbollah, and U.S. Defense Secretary Robert Gates accused the Shiite group of having far more rockets and missiles than most governments in the world.
It is not clear if Obama will raise with Hariri the issue of Hezbollah's weapons.
A Lebanese government official said Hariri will tell Obama that recent Israeli rhetoric is "threatening to create an explosive situation" in the region and would discuss with him ways of protecting Lebanon. He spoke to The Associated Press on condition of anonymity because of the sensitivity of the subject.