Democrats in the Missouri Senate say there is no end in sight for their filibuster over a proposal to add greater religious protections to the state Constitution for some business owners and individuals opposed to gay marriage.

The measure and Democrats' continuing effort Wednesday to block it have ground the Republican-led Senate to a halt and highlighted the national debate over balancing civil rights and religious liberties following last year's U.S. Supreme Court ruling that legalized same-sex marriage.

The measure would prohibit government penalties against those who cite "a sincere religious belief" while declining to provide goods or services of "expressional or artistic creation" for same-sex marriage ceremonies or ensuring celebrations.

Though it doesn't list specific protected businesses, the measure comes after bakers and florists have faced legal challenges in other states for declining to provide services for same-sex weddings.

Sleep-deprived Democratic leaders said late Tuesday evening, after the filibuster stretched to roughly 30 hours, that they're not close to a compromise. They say they are willing to continue stalling, including by taking shifts on the Senate floor and leading discussions on "Star Wars" trivia, to block the measure that they view as discriminatory and that Republicans say they are committed to passing.

Democratic Sen. Jamilah Nasheed, of St. Louis, said she's taking supplements for energy. Republican Senate President Pro Tem Ron Richard on Tuesday evening said he has hasn't slept, aside from a roughly 15-minute nap when he fell asleep in the Senate chamber.

Democratic Kansas City Sen. Jason Holsman said he hasn't left the Capitol since Monday afternoon.

"That means I'm probably pretty rank at this point," Holsman said on the Senate floor. "If I don't get a chance to leave this building until the weekend, then it's, again, worth it."

Republican Sen. Bob Onder sponsored the bill and said he believes "no one should be compelled to make a work with their own hands that's offensive to their beliefs."

His proposal also would shield clergy, places of worship and other religious organizations from being penalized for not participating in marriages involving same-sex partners.

Democrats said they had no problem with protecting pastors from being compelled to perform same-sex marriages but were concerned about the exemptions for some businesses. Some lawmakers invoked images of an era when businesses refused to serve people because of the color of their skin.

"You call it conscious protection; I call it blatant discrimination," said Democratic Sen. Jill Schupp, who offered rainbow-sprinkled cupcakes to senators.

Filibusters in Missouri can be halted by a majority vote, but that procedure is used sparingly in the Senate, which means Democrats in that chamber wield more power than their House colleagues to block legislation. Republican leaders say in this case they prefer to simply wear down the opponents.

Missouri's session runs through mid-May. That leaves plenty of time for the proposal, if passed by the Senate, to also move through the Republican-controlled House. It then would be submitted to statewide voters in either the August primary or November general election.

Republican lawmakers in various states, including Georgia, Florida, Indiana and West Virginia, have pushed similar measures following the U.S. Supreme Court's June decision on same-sex couples marrying.

Onder said his measure is more narrowly crafted than some of those that have faced a backlash, particularly Indiana's, which drew strong criticism from major businesses, prompting lawmakers to revise it. That hasn't convinced Democrats, who say even Onder's more limited policy isn't needed in Missouri.

Missouri's largest statewide business organizations have taken no position on the measure, though the St. Louis Regional Chamber has raised concerns.

Some businesses have opposed it. Among the largest of those is the St. Louis-based agricultural firm Monsanto, which called on other businesses to join it "in speaking out against discrimination here in our home state."

The filibuster marked the longest continuous debate in recent Missouri history. Four Senate Democrats — including current U.S. Rep. William Lacy Clay Jr. — led a 38-hour filibuster spread over five legislative days against an abortion bill in 1999. That bill ultimately passed the Senate.

Republican Senate leaders said they are committed to passing the religious-protection measure. Republican House Speaker Todd Richardson said lawmakers feel an urgency to act this election year; otherwise, the amendment, which would require voter approval, might have to wait until the 2018 ballot.

Missouri is one of more than 20 states with religious objection laws already in place. Current law bans state and local government agencies from substantially limiting a person's right to follow their religious beliefs unless there is a compelling reason to do so.