Tennessee Governor Bill Lee has announced his intention to enact some of the strictest abortion laws in the US.

Sweeping new legislation will include banning women from undergoing an abortion once a fetal heartbeat has been detected.

This occurs about six weeks into pregnancy, before many women know that they're pregnant.

“We're taking a monumental step forward in celebrating, cherishing and defending life,” the Republican governor said on Thursday, surrounded by dozens of state representatives from his party.

“I'm proud to be joined by members of the General Assembly who have helped lead the way in this important effort.”

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Many politicians are up for reelection later this year and see this as a key issue for conservative voters.

Mr Lee plans to introduce legislation in the near future. Similar foetal heartbeat legislation has been enacted in other states, for example Mississippi and Georgia, but has been blocked by legal challenges.

While legal challenges have prevented implementation, supporters of these bills want lawsuits to advance through the courts up to an increasingly conservative US Supreme Court.

This could result in the end of the constitutional right to abortion.

Tennessee pursued a heartbeat abortion ban in 2019 but it failed through fears that the courts would strike down new restrictions as they had in other states.

While that bill passed the House it did not receive support from Senate Speaker and Lieutenant Governor Randy McNally, who said at the time: “We’re trying to construct a law that won't get us into court on the losing side.”

Instead he supported a "trigger ban" bill that would automatically outlaw abortion statewide if the Supreme Court overturned Roe v. Wade, the 1973 decision that legalised abortion.

It is felt that the new legislation will be more legally sound than the 2019 bill, and that has convinced wary politicians, including Mr McNally, to reverse their stance.

Mr McNally joined Mr Lee on the stage for the announcement and tweeted that he is “ecstatic” to support the bill and that he supports the initiative “wholeheartedly and without reservation”.

The new legislation differs from the 2019 bill in that it includes other abortion restrictions and a severability clause.

The Tennessean reports that this includes a contingency in which bans on abortion at eight, 10 and 12 weeks would automatically kick in if the heartbeat provision is struck down.

Mr McNally said: “The destination has always been clear. The issue has been identifying the proper vehicle. We now have the proper vehicle. This comprehensive, tiered approach is our best chance of advancing the cause of life without sacrificing the gains we have made.”

The bill also includes be a ban on abortion for women seeking to terminate a pregnancy because of the gender, race or disability of the foetus.

Governor Lee says that he wants to require women seeking an abortion to be shown an ultrasound of the foetus before they can receive the procedure.

Other specific details about the proposals remain largely unknown. Mr Lee acknowledged during the unveiling of his plans that legislation was still being drafted and was yet to be finalised.

Democrats and abortion rights supporters have announced their opposition.

Mary Mancini, chair of the Tennessee Democratic Party, tweeted: “No politician, @GovBillLee, should be in the middle of the decision to end a pregnancy, choose adoption, or raise a child. Those decisions must be left to a woman, her family and her faith, in consult with her doctor or health care provider.”

Francie Hunt, executive director of Tennessee Advocates for Planned Parenthood, described the legislation as “blatantly unconstitutional”.

“I'm so blown away by the intent behind it, which is basically a power grab over our bodies,” she added.

Efforts to restrict access to abortion have recently surfaced in many states. On Tuesday, the federal government took Ohio's side in a lawsuit over a state law prohibiting doctors from performing abortions based on a foetal diagnosis of Down syndrome.

The disputed law is among nearly two dozen abortion restrictions that Ohio has enacted under the most recent two administrations.

State Republicans also proposed a law that would force physicians to reimplant ectopic pregnancies — a procedure derided as impossible by the medical community.

In spite of this legislative push at the state-level, the majority of Americans want abortion to remain legal.