The Hamas organization says Israel is refusing to release the "heaviest" prisoners as part of a possible prisoner exchange deal. The movement's official website on Tuesday mentioned the names of Marwan Barghouti, Ahmed Saadat, Ibrahim Hamed and Abdullah Barghouti.

Abu Ubaida, a spokesman for Hamas' military wing, the Izz al-Din al-Qassam Brigades, said that there was no news on the talks aimed at securing kidnapped soldier Gilad Shalit's release.

Ubaida denied an earlier report by the al-Arabiya network that Hamas has decided to reject Israel's latest offer for a prisoner swap. "We still don't have an answer for the German mediator," he said.

Hamas reiterated that the discussions continue and that the movement was thoroughly examining the Israeli formula. According to a source in Gaza, the reservations presented by Israel will make it very difficult for Hamas to accept and at least one more round of talks is expected, "before we know whether the deal has reached a deadlock and shifted to a prolonged freeze, or whether we could reach a breakthrough which will allow its execution in the coming weeks."

A Hamas source told Ynet earlier that the movement would not be able to accept the deal following the Israeli reservations. "There are too many candidates for deportation, there are too many prisoners that Israel refuses to release and all this will make it difficult for us to approve the deal," he said.