Germany's foreign intelligence agency has reached an impasse in its efforts to secure the release of Israeli soldier Gilad Shalit, who has been held captive in the Gaza Strip since 2006. The chief negotiator for the Palestinian militant group Hamas has told German news magazine Spiegel that he is no longer willing to take part in talks.

Mahmoud al-Zahar, 64, is sitting in an armchair in the corner of a huge room on the ground floor of his house in the Tel al-Hawa neighborhood of Gaza City. On the other side of the room stands a massive desk, and beyond that a Toyota off-road vehicle. This space serves al-Zahar as a reception room, an office and a garage, all rolled into one. Al-Zahar looks like a lonely man.

He feels betrayed by Israel's Prime Minister Benjamin Netanyahu. In the spring of last year, Netanyahu asked Germany's foreign intelligence agency, the Bundesnachrichtendienst (BND), to act as a go-between in the negotiations with the militant Islamist group Hamas over the possible release of the soldier Gilad Shalit, who was abducted and taken to the Gaza Strip in 2006. Al-Zahar, who is a senior Hamas leader in the Gaza Strip, became the BND's contact person on the Hamas side. Now he has had enough. "I am not ready to negotiate anymore," al-Zahar told Spiegel.

Al-Zahar had received the German negotiators countless times in the Gaza Strip. In December they agreed on a deal: In exchange for the Israeli soldier, 1,000 Palestinians were to be released from Israeli prisons. Netanyahu's negotiator, Hagai Hadas, also indicated his agreement. "Everything was ready to sign," says al-Zahar. He says he traveled to Damascus to convince Khaled Mashaal, the exiled political leader of Hamas, to approve the deal. That was no easy task, al-Zahar says. He argued in favor of a compromise because the German mediator sent signals that Israel would agree to the deal. "I invested so much time, I once even sacrificed the Friday prayer because I was busy working for a compromise," he recalls.