ATLANTA – Republican Gov. Brian Kemp signed an anti-abortion bill Tuesday that is one of the most restrictive in the country and will likely be challenged in court.

The "fetal heartbeat" bill makes it illegal to receive an abortion once a heartbeat is detected in the womb, which happens around six weeks.

"As you all know Georgia is a state that values life," Kemp said as he was signing the bill. "We protect the innocent. We champion the vulnerable. We stand up and speak for those who are unable to speak for themselves."

The law has stirred up opposition among Democratic lawmakers and abortion rights advocates. Critics argue that many women don't know they're pregnant at six weeks and that six weeks is too tight of a window for women to get an appointment with doctors, come up with the money for an abortion, and receive proper care.

The current state law allows abortions up to the 20th week of pregnancy. The new law would take effect Jan. 1, 2020.

The American Civil Liberties Union, Planned Parenthood Southeast and the Center for Reproductive Rights say the law is unconstitutional and plan to file a legal challenge this summer.

Andrea Young, executive director of the ACLU of Georgia, said she expects a Georgia judge will overturn the law.

"We stand with women and we stand with women's rights to make these personal and intimate decisions about when and whether to have or expand a family," Young said. "And I say that as a mother, a grandmother of a granddaughter, that women have got to have these rights for themselves."

Staci Fox, the president and CEO of Planned Parenthood Southeast, said she has “one message for Gov. Kemp: We’ll see you in court.”

State Rep. Ed Setzler, a Republican from the Atlanta suburbs who authored the bill, said the law is about protecting the human rights of unborn children.

The bill, Setzler said, looks to strike a balance between the challenges women face with unplanned pregnancies and the "fundamental right to life."

"This bill is scientifically sound, legally sound, it passes the common sense test," Setzler said Tuesday.

The heartbeat bill's exceptions include cases that involve rape or incest when the woman files a police report. It allows for abortions when a fetus is determined not to be viable or the mother's health is in jeopardy.

The law also permits mothers to collect child support from the father to help cover the costs of her pregnancy and permits parents to claim their unborn child as a tax deduction.

Republican state lawmakers across the country say they are passing strict abortion bans in an attempt to get the landmark 1973 Roe v. Wade decision, which made abortion legal nationwide, overturned.

Mississippi, Ohio and Kentucky have all passed laws that would ban most abortions after a heartbeat is detected.

Alabama lawmakers are considering a bill that would ban nearly all abortions in the state at any stage of the pregnancy unless the mother’s health is in jeopardy.

Republican lawmakers in several other states, including Tennessee, South Carolina, Missouri, Texas, Louisiana, West Virginia and Florida are also considering heartbeat bills.

The Georgia bill had awaited Kemp's signature since April when state lawmakers passed it.

Kemp campaigned on a promise to support anti-abortion legislation. He specifically said he would sign a fetal heartbeat bill, calling the law "common sense."

According to the Guttmacher Institute, a research group that supports abortion rights, about 33,000 abortions were provided in Georgia in 2014.