JERUSALEM - Mohammed Dahlan, one of the most powerful figures in the Palestinian security system, offered his resignation to Yasser Arafat, a senior Palestinian official said Monday.

The offer came as Arafat forms a new Cabinet to replace the one that resigned Sept. 11, just before the Palestinian parliament was to vote no confidence in his government. Palestinian sources said Dahlan hoped to be appointed Interior Minister, but that job was being offered to others.

Dahlan was not available for comment.

Israel Radio reported that Dahlan was unhappy with the slow pace of reforms in Arafat's administration.

The official, speaking on condition of anonymity, said Dahlan sent a letter of resignation from his post as Arafat's security adviser several days ago, but Arafat hasn't responded.

Until May, Dahlan was the head of Preventive Security in the Gaza Strip, resigning around the time Arafat was putting together a new Cabinet. There were reports then that Dahlan wanted to be appointed Interior Minister in charge of all the security branches, but Arafat gave the job to retired Gen. Abdel Razak Yehiyeh.

When Israel-Palestinian security contacts were taking place, Dahlan was a frequent participant. The high-level talks have stopped in recent months amid ongoing violence.