Gilad Shalit - Egypt has been leading talks that could lead to his release
Israel will not agree to a truce in Gaza unless an Israeli soldier held by Palestinian militants is freed, Israeli Prime Minister Ehud Olmert has said.
Gilad Shalit was captured by Palestinian militants in 2006.
There have been reports that Egypt was close to brokering a long-term truce between Hamas and Israel.
A punishing three-week Israeli assault on Gaza aimed at stopping militant rocket fire on Israel ended with separate ceasefires in January.
The uneasy calm has been punctuated by exchanges of fire between the two sides.
"The position of the prime minister is that Israel won't reach any arrangement on a truce before the release of Gilad Shalit," Mr Olmert's office said in a statement.
Prisoner swap talks
On Thursday, Hamas officials said they expected a truce with Israel to be announced within days.
Any truce is expected to see Israel gradually open the borders to Gaza, ending the blockade it has enforced since Hamas seized control of the territory in mid-2007.
In return, Israel wants to see an end to weapons smuggling and attacks from Gaza.
Moussa Abu Marzouk, a deputy leader of Hamas, said his group had agreed to the terms of an 18-month ceasefire with Israel and that he expected it would be announced within 48 hours.
But Israel reportedly wants any ceasefire to be open-ended.
Separately, Egypt has also been leading negotiations on a prisoner swap that would see Cpl Gilad Shalit released in exchange for several hundred Palestinians held by Israel.
Hamas has refused to link the release of Cpl Shalit with the proposed ceasefire.