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The 12-year-old girl said she had been raped by a foreign soldier, one of many who had come to Central African Republic to calm sectarian violence. So the military commander brought her in front of a dozen of his soldiers and asked: Can you identify him?

She could not. And with that, the rape investigation was closed.

A new push against what the U.N. secretary-general calls the "cancer" of peacekeeper sexual misconduct, after the issue flared again last week, has a troubling weakness: Countries' lack of interest in prosecuting their troops who serve in U.N. missions, even though the responsibility is theirs alone.

Sometimes, U.N. officials and observers say, little or no effort is made.

"Of course, the girl was terrified," said Francoise Bouchet-Saulnier, the legal director of Medecins Sans Frontieres, who described the encounter and said it wasn't unique. The girl does not blame a U.N. peacekeeper for her sexual assault — multiple peacekeeping forces have been in the country — but four other children the organization has treated in the country's capital, Bangui, do.

The latest case emerged last week, when Amnesty International accused a U.N. police officer, part of a group from Rwanda and Cameroon, of raping a 12-year-old Muslim girl.

Fed up after a series of similar allegations, the U.N. Secretary-General Ban Ki-moon fired the head of the peacekeeping mission, a first. He also announced measures to pressure member states for accountability, including the suspension of payments to countries for troops who face credible allegations of misconduct.

On Monday, the U.N. mission in Congo tweeted a series of warnings, including an image of a girl on a bed next to a peacekeeper uniform with the words, "No sex with children!" The tweet was later deleted.

The U.N. has no standing army to police some of the world's most vulnerable areas. It relies on 105,000 troops and police largely contributed by developing countries from Africa and South Asia, who appreciate the $1,000-plus per person per month they receive in return.

"Too many incidents go unreported," Ban told a special meeting of the Security Council last week. "Too few cases are prosecuted. ... A failure to pursue criminal accountability for sexual crimes is tantamount to impunity." The U.N. defines sexual abuse as "actual or threatened physical intrusion of a sexual nature," and it prohibits "exchange of money, employment, goods or services for sex."

Getting member states to pursue cases has been a challenge.

This summer, the U.N.'s internal oversight office reported that several countries hadn't said whether they planned to investigate alleged sexual misconduct by their peacekeepers, even though they're supposed to say so within 10 days. The list included both Rwanda and Cameroon, as well as Ecuador, Gambia, Guinea-Bissau, Mali, Vanuatu, Zambia, Guinea and Uganda.

Though more countries have been making efforts to investigate, "standards applied were seen as varying greatly, with some considered very poor," the report said. Senior officials in peacekeeping missions saw countries' investigations as unreliable and "powerfully motivated to exonerate their personnel."

In a rare example of naming names, the report listed the countries, 31 of them, whose peacekeepers faced substantiated allegations of sexual misconduct from 2010 to 2013. South Africa had nine allegations, followed by Uruguay with eight and Nigeria with seven. An allegation can be against multiple people, and there's no way for the public to know how many are accused.

Even when allegations are substantiated, often no action is taken. In 2013, the most recent year for which such data was available, countries punished their troops or police in just over half of such cases. Of the 16 cases, the U.N. repatriated people in 12. Countries then jailed their citizens in five cases, dismissed them in two and demoted or suspended them in two, as of the end of last year.

In two instances of credible allegations of child sexual abuse, including the abuse of a half-dozen children in Haiti by multiple U.N. police officers, peacekeepers were sent home but no punishment was listed. The data did not name peacekeepers' countries.

In Central African Republic, a dozen allegations of sexual misconduct have been received since the mission there was established in April 2014, the peacekeeping office in New York says. Investigations continue in nine cases.

The U.N. says it has no way to vet for past misconduct each of the more than 200,000 people who rotate through six-month peacekeeping stints every year. A Misconduct Tracking System is limited to certain officers and civilian staffers. A report by Ban earlier this year on tackling sexual misconduct says ways to vet troops and police "are under development."

Stretched for resources with a record number of peacekeepers in the field, the U.N. has hesitated to upset member states by announcing the countries whose troops or police are accused of wrongdoing, until now. On Thursday, Ban announced his intention to do so.

When countries don't act on allegations, U.S. U.N. Ambassador Samantha Power told reporters, "I think it's extremely important that that be known."

Bouchet-Saulnier, the MSF legal director, appreciated the U.N.'s pressure for accountability but urged more speed. "Victims are so desperate and left alone that it's not easy to keep them interested, and even alive," to pursue their cases, she said.

Ban's report earlier this year indicated that some countries are not yet motivated to change.

Even though member states, as part of signed agreements to contribute peacekeepers, now promise to give the U.N. chief regular updates on misconduct cases, "some do not respond at all."