Kamala Harris and Donald Trump have taken a detour from barnstorming the battleground states that will decide November's election with stops in Texas, a conservative state that was the first to implement a near-total abortion ban.

Texas hasn't backed a Democratic president since 1976, and Republican Trump is almost certain to win the state's 40 electoral college votes.

But Democrats are betting it will provide a powerful backdrop for Vice President Harris to talk about abortion rights in the final days before the November 5 election.

Superstar singer Beyoncé who was born in Houston, fired up the crowd on Friday by introducing Harris, who came on stage to a recording of Beyonce's song Freedom, which has made her campaign anthem. She did not sing, however.

Harris spoke about the danger former president Trump and Republicans could present to abortion rights across the country if he's elected, a campaign source said, and be joined by women who have suffered after Texas' anti-abortion regulations were passed and their family members.

"Texas, what is happening across this state and our country is a health care crisis, and Donald Trump is the architect of it," Harris said.

Texas implemented a first-of-its kind law in September 2021 that banned abortion after six weeks and allowed anyone to sue abortion patients in violation and those who assisted them.

The US Supreme Court, with a conservative majority formed by Trump's judicial appointments, allowed the law to stand, and then gutted federal abortion rights by overturning Roe v. Wade in June 2022.

In between personal stories of abortion-related tragedy, and before Beyonce took the stage, the rally took on the air of a dance party, with people swaying and singing along to a DJ.

While Beyoncé appealed to a younger crowd, 91-year-old Willie Nelson showed earlier in the event that he still has cachet in his native Texas.

"Are we ready to say Madam President?" Nelson asked the crowd before launching into Mammas Don't Let Your Babies Grow Up To Be Cowboys, to which the audience sang along.

He closed with On the Road Again.

(Country music legend Willie Nelson, 91, is right behind Kamala Harris for US President. (AP PHOTO)

Trump was also campaigning in Texas on Friday, making a stop in Austin to record an episode of The Joe Rogan Experience, a popular podcaster with tens of millions of social media followers, most of them men.

After a three-hour interview with Rogan in Texas, Trump arrived late to a rally in battleground state Michigan.

"We've got a war going and she's out partying," Trump said Friday night, a reference to Israel's attacks on Iran.

Trump has lost ground with women voters since Harris became the Democratic candidate, polls show, although the two are in a tight race in the battleground states.

(Kamala Harris has reiterated the dangers of a second Donald Trump term as US president. (AP PHOTO)

Harris led Trump by 49 to 36 per cent, or 13 percentage points, among women voters in a Reuters/Ipsos poll published late in August, compared to her nine-point lead in polls conducted in July.

Trump has taken credit for appointing the justices who helped overturn Roe v. Wade.

The majority of Americans disagreed with the Supreme Court's overturning of Roe, which fuelled a wave of Democratic wins in the 2022 midterm elections and left Republicans scrambling to find a winning message on the issue.

(Donald Trump kept his Michigan rally crowd waiting three hours while he did the Joe Rogan podcast. (AP PHOTO)

A recent survey of women voters by KFF, a health policy research and news organisation, found that abortion was the top issue for women voters under age 30.

Harris led the Biden administration's reproductive rights initiatives and has made the issue a cornerstone of her presidential campaign.

Democrats have highlighted personal stories to show the impact of abortion being almost entirely banned in 16 states.

By Trevor Hunnicutt, Gabriella Borter and Georgina McCartney in Houston