"In the meetings that we have held in the last 48 hours with the Israelis, our teams told us that Israel may change their minds about pulling out of the north West Bank," Yussef told reporters on Tuesday after a meeting with General William Ward, the US pointman on Palestinian security reforms.
"This is a source of worry and we told General Ward and the international groups we met today about our concerns."
A senior Israeli government official said there was no question of reversing the decision to leave the four isolated settlements but said the army would retain the right to take action against fighters in the area after the pullout.
"After the withdrawal, the area will be administered by the Palestinians but the army will remain in the surrounding area with the possibility of intervening" against armed groups, the official said on condition of anonymity.
Palestinian officials have previously expressed unhappiness about the Israeli reluctance to hand over full administrative and security control of areas around the four settlements in the Jenin area of the West Bank.
"After the withdrawal, the... army will remain in the surrounding area with the possibility of intervening"
Senior Israeli government official
As part of preparations for the pullout, the Israeli army declared two of the four settlements a closed military zone on Tuesday.
Meanwhile, an ailing elderly Palestinian man died on Tuesday after the ambulance taking him to hospital was stopped at an Israeli checkpoint in the West Bank, Palestinian medical sources said.
Mohammad Amin Tayin, 73, from the village of Al-Fonduq, south of Nablus, was being taken to hospital when Israeli soldiers manning a checkpoint stopped the ambulance for half an hour.
Tayin died from a heart attack, the sources said. The Israeli army told reporters that it was trying to verify the incident.