ATLANTA (AP) - A new federal lawsuit filed in Atlanta seeks to block a Georgia law that bans most abortions, saying it's unconstitutional.

Lawyers with the American Civil Liberties Union, Planned Parenthood and the Center for Reproductive Rights filed the lawsuit Friday on behalf of Georgia advocacy groups and abortion providers. The law is among the nation's most restrictive abortion laws.

It would effectively ban the procedure at around six weeks of pregnancy before many women know they're pregnant. It does allow for some limited exceptions.

The ban is set to take effect Jan. 1 if it's not blocked by a judge.

Georgia Gov. Brian Kemp acknowledged when he signed the measure into law in May that a court challenge was likely. But he said he was undeterred.