Hamas said Monday that a prisoner exchange agreement with Israel could be concluded in December, as negotiations for the release of captive soldier Gilad Schalit dragged on longer than initial media reports had anticipated. The announcement came as a German negotiator arrived in the Gaza Strip from Israel, to resume talks with Hamas on the deal. Sources close to Hamas said the German official, whose identity was unknown, held a series of discussions with senior Hamas representatives. Fathi Hammad, minister of the interior in the Hamas government, hinted that the deal with Israel could be signed on December 14, the 21st anniversary of the founding of the Islamic movement. He also did not rule out the possibility that the agreement would be reached close to December 27, which marks the first anniversary of Operation Cast Lead. "We want either date to mark the day when hundreds of Palestinian prisoners are released from Israeli jails," Hammad told families of Palestinian inmates held in Israel. Hamas spokesman Sami Abu Zuhri said he had no information about the German mediators and refused to provide any details about the status of the negotiations. But senior Hamas officials said the movement is still sparring with Israel over the names of 50 prisoners it wants released in exchange for Schalit, signaling there were still significant gaps before completing the anticipated deal, the Associated Press reported. The officials said Israel is still balking at including prominent political leaders and top Hamas militants it holds. The officials spoke on condition of anonymity because of the sensitivity of the German-mediated negotiations. At the top of the contested list is top Fatah operative Marwan Barghouti, who is serving five consecutive life terms for his role in shooting attacks that killed four Israelis and a Greek monk. A German mediator has been based in Jerusalem for the past three months, shuttling regularly to Gaza City to broker terms of the agreement, a Hamas official told the Associated Press. He said that in addition to the 50 disputed names, the sides are also arguing over Israel's demand that some 130 people be deported after their release. Hamas wants that number reduced. Mohammed Nazal, a senior member of Hamas' exiled political leadership based in Damascus, said progress was being made. "The German mediator is very active, very professional. He spends his time shuttling between the Palestinians and the Israelis, negotiating over every single name on the list," he said. On Sunday, in a response to a petition to the High Court of Justice, the state said the government planned to release 980 prisoners in exchange for Schalit, of which a list of 450 would be determined with Hamas. A second list of 530 Palestinian prisoners would be set by Israel, the state said. In hopes of finally seeing his son, who has been held by Hamas in Gaza since June 2006, Schalit's father Noam continued lobbying government ministers on Monday to support the prisoner swap, once Israel and Hamas agree on a prisoner list. He spoke with Likud ministers Silvan Shalom, Yisrael Katz and Moshe Ya'alon as well as Israel Beiteinu minister Sofa Landver. On Tuesday he is expected to speak with Likud ministers Gideon Saar and Limor Livnat, as well as Israel Beiteinu Minister Yitzhak Aharonovitch. On Wednesday he is set to meet with Interior Minister Eli Yishai of Shas. Schalit told reporters on Monday that until his son returns, he would not know if his conversations had been successful. Tovah Lazaroff and AP contributed to this report.