Karzai has come under pressure from his Western allies for signing a law that Western media reports say means Shiite women cannot refuse their husbands sex nor leave the house without his permission.
NATO leaders meeting in the French city of Strasbourg were united in expressing their strong disapproval, with British Prime Minister Gordon Brown saying he had phoned Karzai to express his "grave concern."
The law "risks putting Afghanistan back to its past rather than towards it democratic future where men and women are treated equally," Brown told reporters.
French President Nicolas Sarkozy said it was a "unanimous demand" by NATO members that "women's rights are defended and respected by the Afghan government."
"We are there (in Afghanistan) to defend our values.... We refuse to compromise on these values," Sarkozy said in a closing news conference.
Sarkozy's co-host for the summit, German Chancellor Angela Merkel, called the law "unacceptable" and for it to be scrapped.
"Everyone in Afghanistan should have the right to live in freedom," Merkel said.
Canadian Prime Minister Stephen Harper said there was "enormous pressure" on the Afghan government to revoke the law.
"The equality of men and women goes to the heart of our value system and our engagement in that country and our opposition to the Taliban and the Taliban government," he said.
A senior Italian defence official meanwhile said on the sidelines of the NATO summit that Rome might bring home the 30 female members of its 2,665-strong military contingent in Afghanistan in protest.
In Kabul, Karzai said concerns may be because of mistranslation or misinterpretation, and that if any cause for concern were found the ulema (religious clerics) would be consulted and the law sent back to the parliament.
"Issues that have been mentioned in the Western media, such things are not in our law," he said. "But the minister of justice will study the whole law, every item of it, very, very carefully."
He said anything found contrary to Afghanistan's post-Taliban constitution -- which enshrines gender equality -- would "no doubt" be corrected.
The Shiite Personal Status Law covers Afghanistan's Shiite minority, which makes up about 15 percent of the population, and was drafted on their request because of certain differences with Sunnis about Islamic Sharia law.
The UN human rights chief in Afghanistan, Navi Pillay, on Thursday urged the Afghan government to revoke new legislation, saying it was "reminiscent of the decrees made by the Taliban regime".
The ultraconservative 1996-2001 Taliban government stopped girls from going to school and women from working, and forced women to wear all-covering burkas and have a male relative as an escort when they left the house.
Under the new regulations, Shiite women would be forbidden from leaving their homes except for "legitimate purposes", Pillay's office said.
They are also banned from working or receiving education without their husbands' permission, it said.
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