Anglican Archbishop Desmond Tutu said Thursday he is as committed to abolishing child marriage around the globe as he was to fighting apartheid in South Africa.

Tutu made his remarks at the launch of U.N. campaign to end child marriage by 2030, in a bid to free girls from poverty, ignorance and oppression at the hands of their husbands.

The U.N. Population Fund says about 37,000 girls under age 18 are being married off daily, at a pace rising toward 14.2 million a year by 2020, and 15.1 million a year by 2030, if the trend is not curbed.

"I give my commitment to work for the abolition of child marriage. That commitment is my dream, and I want it to be equal to the commitment that I had when I fought against apartheid," said Tutu who is one of the group of "Elders" who advise the U.N. and governments on social problems.

The U.N. agency said the problem is mainly concentrated in South Asia and sub-Saharan Africa, where girls as young as 5 or 6 are married off, but its study, "Marrying Too Young," focused on the developing world, and did not include statistics on child marriage in China, Russia, Western Europe, Canada or the United States.

The U.N. Population Fund's executive director, Dr. Babatunde Osotimehin, called for all nations to set a mandatory marriage age of 18.

Many U.S. states allow children of 16 or 17 to marry with parental permission or a court order; some allow marriage at 15 or 14 in special circumstances.

In South Asia, 46 percent of women aged 20-24 had married before they were 18, the U.N. study found. In Bangladesh, the rate was 66 percent.

In sub-Saharan Africa, 37 percent of women aged 20-24 had married before they were 18, the study found. Niger had the highest rate, at 77 percent.

Girls under 15 are five times more likely to die in childbirth than women in their 20s, and girls age 15-18 are twice as likely to die, the U.N. study found. The children of girl brides are 60 percent more likely to die by their first birthday than children with mothers over age 19.

"Let us help those who are already married to lead more fulfilling lives. All members of society will benefit when we let girls be girls, not brides," said U.N. Secretary-General Ban Ki-moon.

"By 2020, 142 million innocent young girls worldwide will be separated from their friends and family, deprived of an education and put in harm's way because of child marriage," Ban said, adding that young girls are unable to safely bear pregnancies, and their newborns are at risk of low birth weight.

In Washington, U.S. Secretary of State Hillary Clinton took time out to observe the launch of the U.N.'s first "International Day of the Girl Child."