The US Supreme Court confronted the nation's homelessness crisis on Monday, weighing whether a ban on sleeping in public is cruel and unusual punishment.

The case centres on the small town of Grants Pass, Oregon, but has broad implications for cities of all sizes.

The court's conservative majority appeared sympathetic to the argument that questions around homelessness should be left to local governments.

Its decision is expected in early summer.

Grants Pass has barred camping or sleeping on public property or in city parks, defining "campsite" as any place where "bedding, sleeping bag or other material used for bedding purpose, or any stove or fire is placed" .Violators may be fined $295, or face 20 days in jail for repeat offenses.

The city, with a population just under 40,000 people, said it enforced its camping ordinances with "moderation", issuing more than 500 citations over a five year period from 2013 to 2018.

Still, in 2018, five people experiencing homelessness in Grants Pass sued the city on behalf of its homeless population, arguing the ban violated the US constitution's eighth amendment, which protects against cruel and unusual punishment.

Grants Pass countered, saying the fines and possible jail time were not cruel but necessary deterrents for homeless encampments. A lower court, the San Francisco-based 9th US Circuit of Appeals disagreed, ruling the ordinances were unenforceable.

But on Monday, over more than two hours of arguments, the Supreme Court's justices conservative majority seemed to agree with arguments made by Theane Evangelis, a lawyer for Grants Pass, that homelessness and homeless encampments were "complicated policy questions" best left to legislators, not judges.

"Why do you think these nine people are the best people to judge and weigh those policy judgments?" Chief Justice John Roberts asked at one point, referring to himself and his eight fellow justices.

But the three liberal justices were more concerned with how homeless people are treated, noting sleeping is a basic human need.

"Where are we supposed to put them if every city, every village, every town lacks compassion and passes a law identical to this? Where are they supposed to sleep?" Justice Sonia Sotomayor asked Ms Evangelis. "Are they supposed to kill themselves, not sleeping?"

The justices will issue their decision in June or July.