An independent study of the Palestinian security forces in Gaza and the West Bank has concluded that they are weak, ill-equipped and divided.
It also says that the Palestinian Authority (PA) forces are overstaffed and outgunned by militant groups.
The report comes weeks before the PA takes over responsibility for Gaza.
The study, by the Strategic Assessments Initiative, was drawn up to identify ways in which international donors can help the security forces reform.
It is the first independent, in-depth analysis of the Palestinian security forces since the death of Yasser Arafat, and was financed by the Dutch and Canadian governments.
It was prepared in close co-ordination with Lt Gen William E Ward, the US official in charge of the effort to overhaul the Palestinian Authority and its security apparatus.
The lack of equipment includes shortages of ammunition, of means of communication beyond mobile phones and of all-terrain vehicles.
Other problems include the continuing power of personalities and clans, which often create alternative, informal chains of command and weaken the authority of the man in overall charge, Palestinian Authority Interior Minister Nasser Yousef.
BBC Jerusalem correspondent Nick Thorpe says the problems are closely tied to the history of the conflict in recent years – the destruction of the Palestinian police infrastructure by the Israelis since the start of the second intifada, or Palestinian uprising, in 2000.
Continuing attempts to streamline the forces are praised by the report, but the overall picture is disturbing. It says the Palestinian forces are caught between far better equipped Palestinian militant groups on the one side and the Israeli army on the other.
Risks to disengagement
The report sees the greatest risks to a successful Israeli disengagement coming from rocket or mortar attacks carried out by Islamic Jihad or other smaller, Palestinian militant groups.
It also points to the risk of the risk of Israeli settler incursions intended “to provoke a violent Palestinian reaction” and tie up the Israeli army, and from the continuing lack of clarity about the Israeli army’s intentions for the period immediately after disengagement.
In recent weeks, there have been several clashes between Hamas and Palestinian security forces trying to prevent the militants in Gaza from firing missiles into Israel.
Correspondents say the Palestinian forces have tended to come off worse.
Israel is due to withdraw its settlers and the soldiers that protect them from Gaza, beginning in mid-August. Israel will maintain control over Gaza’s borders, coastline and airspace.
About 630 settlers will also be removed from four small West Bank settlements.
Israel has occupied Gaza and the West Bank since 1967.