The bill would ban abortions once a fetal heartbeat is detected, typically in the early weeks of pregnancy.

The ACLU of Tennessee has said it will file suit if the measure becomes law.

Some abortion opponents worry an expensive legal battle over the measure would end in defeat.

Tennessee's Catholic bishops have taken the unusual step to publicly oppose a bill that would ban most abortions in the state after a fetal heartbeat is detected.

"While we wholeheartedly support the intention of the 'Heartbeat Bill' being considered by the Tennessee legislature, we must also be prudent in how we combat the pro-abortion evil that dwells in our state," a joint statement by the leaders of the Nashville, Memphis and Knoxville dioceses said.

The statement was published Tuesday in the The Tennessee Register, a Catholic newsletter.

The opposition to the measure by the state's Catholic Church leadership underscores the more pragmatic approach to curbing abortion adopted by opponents in recent years.

Legal challenges give abortion opponents pause

Should the heartbeat bill become law, it faces certain legal challenges that could prove costly to state taxpayers, who would foot the bill for litigation, and could ultimately deliver a defeat to anti-abortion advocates.

The Tennessee attorney general called a similar measure that failed in 2017 "constitutionally suspect" because it would run contrary to Roe v. Wade, the landmark Supreme Court decision establishing the right to an abortion.

The American Civil Liberties Union of Tennessee has said it will file suit if the measure becomes law.

Tennessee Right to Life, the state's chief anti-abortion group, also opposes the measure in its current form.

"Given the field of legal realities that we must consider, we believe it would not be prudent to support the 'heartbeat bill' knowing the certainty of its overturning when challenged, in addition to the court-ordered fees that would be paid to the pro-abortion plaintiffs," the statement from Knoxville Bishop Richard Stika, Nashville Bishop Mark Spalding and Archbishop Joseph Kurtz, who is overseeing the Memphis diocese from Louisville until a new bishop is installed.

Heartbeat bill has governor's support

The heartbeat bill, however, has quickly sailed through the bill-making process, gaining the vote of every Republican on each committee it has come before. The bill continues to move through Senate committees, and now appears likely to make it to a final vote in the Republican-majority legislature. Gov. Bill Lee has said he supports the measure.

In response to critics of the measure who have cited the likely and expensive litigation to follow its passage, its chief sponsor Rep. Micah Van Huss, R-Jonesborough, has said "we owe it to our taxpayers to use every available resource to save babies' lives."

In their joint statement, the Catholic leaders said "we pray urgent support will be given" to a separate measure known as the Human Life Protection Act. That measure would trigger an automatic ban on abortions in the state should the Supreme Court amend or overturn Roe v. Wade.

That bill, introduced by Rep. Susan Lynn, R-Mount Juliet, and Sen. Delores Gresham, R-Somerville, has not gotten the same momentum in the state's legislature.

The heartbeat measure, proposed by Van Huss and state Sen. Mark Pody, R-Lebanon, would make it a felony to perform an abortion in Tennessee once a fetal heartbeat can be detected — which typically occurs in the early weeks of a woman's pregnancy. The bill includes no exceptions for rape or incest, but does include an exception in the case of a medical emergency.

For complete coverage of the Tennessee General Assembly, subscribe to one of our publications.

Reach Anita Wadhwani at awadhwani@tennessean.com, 615-259-8092 or on Twitter @AnitaWadhwani.