But the moratorium would probably exclude large settlement blocs that Israel wants to retain in a final peace agreement, the Israeli paper Haaretz said.
The Palestinians are demanding that all of the West Bank, which Israel captured in the 1967 six-day war, be included in a future state.
The Israeli prime minister, Ehud Olmert, sent top officials to Washington yesterday to work out exactly what the settlement freeze would entail, Haaretz reported.
It said the move follows US pressure on Israel to issue the declaration as a gesture to the Palestinians, to make up for its refusal to discuss the core issues of a final peace agreement before the conference, which is due to take place in Annapolis, Maryland, before the end of the year.
Israel has said it is willing to discuss the core issues, which include the fate of West Bank settlements, after the conference.
The US wants a demonstration from both sides of their willingness to comply with the road map - a long-stalled peace plan that calls on Israel to freeze all settlement activity.
The Palestinians say they have begun cracking down on militants - a condition of the road map - but Israel says they must go much further.
The Palestinian negotiator Saeb Erekat said it was not good enough to partially-halt settlement activity.
"Israel cannot be selective and say we will expand in some places and not in others," he said. "Settlement activity must be frozen totally. So no games."
Haaretz said Israel would also announce a willingness to dismantle dozens of settlement outposts, as required in the road map.
Settlers launched a campaign yesterday to prevent the government from hampering settlement activity, according to Israeli army radio, though it was not immediately clear how they planned to do this.
Nearly 270,000 Israelis live in settlements in the West Bank. In a report issued earlier this month, the settlement watchdog group Peace Now found that construction is ongoing in 88 of the 122 settlements.
A spokeswoman for Olmert would not comment on the Haaretz report.