The U.N. chief is taking aim at sexual abuse by peacekeepers, "one of my greatest disappointments," saying he will repatriate the troops of countries that don't act on allegations and has already started to suspend payments to countries when allegations are credible.

Ban Ki-moon's statements, obtained Thursday by The Associated Press, are in response to the first comprehensive assessment of peacekeeping in 15 years and largely agree with a high-level panel's suggestions for a major overhaul. The U.N. has more than 105,000 troops and police in 16 missions in some of the world's most dangerous places. Member states contribute the personnel and receive monthly payments in return.

The changes come as President Barack Obama prepares to host a major U.N. meeting later this month aimed at drawing European and other developed countries back to peacekeeping with their funding and skills in intelligence-gathering, engineering, air support and medical care.

Though more peacekeepers have been deployed than ever before, "proliferation of conflict is outpacing our efforts," Ban wrote. It can take several months after a mission is authorized for peacekeepers to arrive. Not everyone comes properly equipped and trained. There is no current system for vetting peacekeepers for past abuses. Peacekeepers have been shown to rarely use force to protect civilians.

This summer's high-profile series of allegations of sexual abuse by peacekeepers, including of minors, in Central African Republic has caused another layer of concern as the U.N. tries to reshape a peacekeeping system that costs about $8.2 billion this year alone.

"I will repatriate contingents where there is a demonstrated pattern of abuse or non-response to allegations of misconduct," Ban's report says.

The report also says that from now on, countries that are repeatedly listed in his annual reports on children and armed conflict, and on conflict-related sexual violence, will not be allowed to participate in peacekeeping.

Troops that refuse to follow orders can now be repatriated. "Uniformed personnel must comply with orders to prevent, deter and protect civilians against attacks," Ban wrote. If not, he will investigate and inform the U.N. Security Council and member states.

By early next year, peacekeeping officials will finalize a plan to establish a "fully functional" rapid-response headquarters on the ground two to three months after the Security Council approves a new mission. Standby units for early deployment are also being planned.

Addressing sexual abuse in particular, Ban is announcing several changes. By the end of this year, "immediate response teams" will be established to gather evidence within 72 hours of an allegation. Investigations, which have averaged a year or more, must be completed within six months. A plan for vetting troops and police for past sexual misconduct will be developed by the end of this year.

Member states have the sole responsibility to prosecute their troops, but a U.N. investigative report released this summer showed that countries can take little action. "I urge member states to hold court-martials in host countries as a measure of visible accountability," Ban wrote.

The U.N. chief again declared his intention to start naming the countries whose peacekeepers have been accused of sexual misconduct — but after consulting with member states on how to do so.

Reflecting that pressure from member states, a U.N. peacekeeping spokesman on Thursday said they were not making public the names of countries whose payments have been suspended over credible allegations of sexual misconduct by their troops.

The issue of sexual misconduct also should be on the agenda when the Security Council meets with troop and police contributing countries, Ban wrote.

The use of force by peacekeepers is another persistent issue, especially in dangerous places like northern Mali. Ban says that when a mission has an explicit mandate to protect civilians, uniformed personnel must do it, even by using force if necessary.

But the U.N. chief warns that peacekeeping is not designed "to impose political solutions through sustained use of force," and that "U.N. peace operations are not the appropriate tool for military counter-terrorism operations." He stressed that political solutions should be the goal.