US intelligence shows that the Libyan strongman "doesn't feel safe anymore" in the capital where he has ruled for over four decades, the Journal quoted a senior US national security official as saying.
However, officials told the Journal they did not see the move as imminent and did not believe Gaddafi would leave the country, a key demand of Libyan rebels who have been battling his forces in a weeks-old stalemate. Gaddafi is believed to have numerous safe houses and other facilities both within the capital and outside of it to which he might relocate.
The news comes as US President Barack Obama faces rising criticism from fellow Democrats and rival Republicans in Congress over his refusal to seek congressional authorisation for the three-month-old military operation.
The Obama administration has said approval under the 1973 War Powers Resolution is not required because US participation in the NATO-led air war does not rise to the level of "hostilities," a logic rejected by critics.
A senior US commander meanwhile said that the North Atlantic Treaty Organisation (NATO) and Libya's African allies had not adequately planned for the aftermath of Gaddafi's possible fall.
"We, the international community, could be in post-conflict Libya tomorrow and there isn't a plan, there is not a good plan," the senior US commander in Africa, General Carter Ham, told the Journal.
He predicted that Gaddafi could fall quickly, and said there may be a need for substantial ground forces in the country to preserve order.