Republicans and Democrats offered competing visions for reproductive rights Friday as the anniversary of the US Supreme Court decision ending nationwide abortion access threw a spotlight on a polarizing issue sure to dominate the 2024 election.

Thousands of religious conservatives gathered for a two-day conference in Washington to hear Donald Trump's main rivals for the Republican presidential nomination try to outflank the frontrunner, who has been criticized for flip-flopping on his position.

And in a split-screen moment in the capital, Democratic President Joe Biden was being feted by powerful family planning groups as he announced an executive order aimed at boosting access to contraception.

"When people want to know where @JoeBiden and @KamalaHarris stand on reproductive freedom, we tell them: they are unwavering," Planned Parenthood, the country's leading abortion provider, said on Twitter.

But a mile or so north of the White House, Republican presidential hopefuls lined up at a plush downtown hotel to berate the Biden administration and compete for the backing of 3,000 evangelicals attending the Road to Majority conference.  

Florida governor Ron DeSantis hailed the six-week abortion ban he signed into law, while ex-vice president Mike Pence challenged every candidate to back a nationwide prohibition.

DeSantis, who is polling in second in the Republican primary, more than 30 points behind Trump, said Florida had delivered on "promoting a culture of life" with his so-called "heartbeat bill," which goes much further than the 15-week ban embraced by moderate Republicans. 

"It was the right thing to do -- don't let anyone tell you it wasn't," DeSantis said in a veiled swipe at Trump, who has criticized the Florida law as "too harsh."

- 'Sanctity of life' -

Pence, who is running a distant third in the Republican primary, told the conference that every candidate should support a ban on abortion that kicks in at 15 weeks of pregnancy or earlier.

"Let me say from my heart, that the cause of life is the calling of our time," Pence said.

"And we must not rest and must not relent until we restore the sanctity of life in the center of American law, in every state in this country."

Trump thrilled conservatives when he appointed three justices to the Supreme Court during his single term in office who voted to strike down a decades-old legal precedent guaranteeing federal abortion protections.

But the religious right has been dismayed by the billionaire former reality TV star refusing to publicly back a nationwide ban even as he takes credit for the court's ruling.

Trump has also warned against tacking too far to the right, and suggested that anti-abortion hardliners were to blame for the poor Republican showing in last year's midterm elections.

Road to Majority -- organized by the Georgia-based, two-million-member Faith and Freedom Coalition -- brings together the major Republican presidential hopefuls on the same stage for the first time.

Trump is due to deliver the keynote address on Saturday -- the one-year anniversary of the Supreme Court's ruling, which made reproductive rights a prerogative of the states.

Since June 24 last year 20 states, mainly in the US south and interior, have enforced bans or strong restrictions on abortion, while liberal-leaning states on the coasts have passed new protections.

- Devout Catholic -

Joining Planned Parenthood in endorsing Biden and his running mate Kamala Harris, NARAL feted the president Friday as he directed officials to ensure private health insurers cover all approved contraceptives. 

Biden and Harris have "done more to defend and expand reproductive freedom than any other administration in history," the abortion advocacy organization said.

Biden is a devout Catholic but in recent years the 80-year-old has taken on the role of the country's top reproductive rights advocate.

After Roe was struck down, he issued several decrees to marginally protect access to abortion as well as announcing new protections for contraception.

The issue of abortion rights crystallizes divisions in the United States and for many voters it is a key factor on election day, a trend that has become more pronounced over the last year.

According to a recent CBS/YouGov poll, 63 percent of Americans oppose a federal ban on abortion.

And in a Gallup poll published earlier this week, 28 percent of registered voters said they chose candidates based exclusively on their abortion stance, a record level.

ft/bgs