SAN’A, Yemen – Some of Yemen’s most influential Islamic leaders, including one the United States says mentored Osama bin Laden, have declared supporters of a ban on child brides to be apostates.

The religious decree, issued Sunday, deeply imperils efforts to salvage legislation that would make it illegal for those under age 17 to marry.

The practice is widespread in Yemen and has been hard to discourage in part because of the country’s gripping poverty. Bride-prices in the hundreds of dollars are especially difficult for poor families to pass up.

More than a quarter of Yemen’s females marry before age 15, according to a report last year by the Social Affairs Ministry. Tribal custom also plays a role, including the belief that a young bride can be shaped into an obedient wife, bear more children and be kept away from temptation.

A February 2009 law set the minimum age for marriage at 17, but it was repealed and sent back to parliament’s constitutional committee for review after some lawmakers called it un-Islamic.

Some of the clerics who signed Sunday’s decree sit on the committee. The group behind the declaration also includes Yemen’s most influential cleric, Sheik Abdul-Majid al-Zindani, whom the United States has branded a spiritual mentor of bin Laden.

In a further challenge to the rights groups pushing for a ban, government officials are reluctant to challenge al-Zindani and other conservative tribal and religious figures whose support they need to hold onto power in the fragile nation.

The religious leaders organized a protest against the legislation Sunday by a group of women. Hidden behind black face veils and robes, the women carried signs that read: “Yes to the Islamic rights of Women.”

“I was married at 15 and have many children now,” said Umm Abdul-Rahman. “And I will marry my daughter at the same age if I decide she is ready for it.”