President Donald Trump's contentious travel ban expires Sunday with little clarity over whether America's door will reopen for travelers from six majority-Muslim countries.

Based on the policy, US embassies or representatives in Syria, Iran, Libya, Somalia, Sudan and Yemen should resume granting visas to their nationals planning to visit the United States for work, study, pleasure or to emigrate.

But some think the Trump administration, determined to stick to his election promise to block Muslims from the country, will extend the 90-day ban at least until the Supreme Court can rule on it next month.

Omar Jadwat, an American Civil Liberties Union lawyer who has argued against the ban in court, said politics, not national security, would likely decide the issue.

"The animating principle for the government throughout has been, the president wants a ban, the president wants to ban as many people as he can, as many Muslims as he can, and we're going to do what we can to make that possible," he told AFP.

"I think that's how we got to where we are now."

- Political uproar -

The ban -- which initially included Iraq and was accompanied by a 120-day block on all refugees -- sparked a political uproar when Trump first announced it on January 27, a week after becoming president.

The ban was frozen by courts after a weekend of chaos at airports and a barrage of lawsuits by immigration advocates and civil liberties groups.

The administration's stated reason was national security: the need to ensure the six countries have adequate vetting procedures for travelers, so as to prevent terrorists from entering the country.

But critics alleged that it amounted to Trump's promised "Muslim ban" which courts agreed was unconstitutional because it discriminated against a single religion.

Several states also sued to block it on grounds that it prevented legitimate visa holders, family members, US residents, students in universities and foreign workers for US companies from entering the country.

After losing challenges in appeals courts, on March 6 the White House unveiled a revised ban, excluding Iraq and exempting people who already had visas. Nine days later that, too, was frozen, by a judge in Hawaii, for largely the same reasons as the original.

Again, the administration lost in two appeals courts, leaving Trump furious and turning to the Supreme Court.

- Trump declares victory -

On July 26 the high court ruled to partially lift the freeze on the ban, while agreeing to hear the White House's appeal to lower court rulings in October.

Trump declared a political and legal victory and shut down visa issuance for the six countries. 

"Great day for America's future Security and Safety, courtesy of the U.S. Supreme Court. I will keep fighting for the American people, & WIN!," he tweeted.

By that time, ironically, the original 90 day ban would have been expired for two months. Arrivals from the six countries had already fallen by more than half due to "extreme vetting" procedures that increased the difficulty of getting a US visa.

The White House has not hinted how it will handle the expiration on Sunday, and advocates for immigrants say they don't know. 

The Department of Homeland Security last week presented a classified report on security issues and vetting procedures for the six countries, which could theoretically lead to an update in the policy -- removing some countries from the ban, for example.

Jadwat says Trump could issue a new executive order that updates but does not end the ban.

"There's a lot of things the government can do, both within the four corners of the order," he said.