The San Francisco 49ers and Kansas City Chiefs clash in a blockbuster Super Bowl showdown on Sunday as Las Vegas stages the American sporting showpiece for the first time.

The glittering gambling capital in the Nevada desert is crackling with anticipation ahead of an NFL championship game that has topped even the usual stratospheric levels of hype.

The romance between pop megastar Taylor Swift and the Chiefs' charismatic Travis Kelce is just one of the storylines of a game that is expected to smash US television viewing records.

Swift is reported to have arrived back in the United States en route to "Sin City" on Saturday after making an 8,900km trans-Pacific dash across the international dateline following a performance in Tokyo on the latest leg of her money-spinning world tour.

The singer will be among a crowd of celebrities, VIPs and high-rollers packed into the 65,000-seat Allegiant Stadium to see if Kelce and the Chiefs can clinch a third Super Bowl crown in five seasons.

The Federal Aviation Administration estimates around 500 private jets will touch down in Las Vegas for the game, while local officials say more than 300,000 visitors have descended on the city for the Super Bowl weekend.

Roulette wheels and slot machines are doing a roaring trade while poker tables in several casinos are staffed by dealers wearing NFL merchandise in a city once shunned by the league due to its association with gambling.

The horde of tourists will flock to nightclubs and celebrity-hosted watch parties being laid on in addition to Las Vegas' regular array of concerts featuring stars such as U2, Adele, Christina Aguilera and Green Day.

Those fans lucky enough to have a ticket for the game, where R&B star Usher headlines the half-time show, have paid handsomely for the privilege.

The cheapest seats available on resale ticketing website Stubhub on Saturday came with a hefty US$5,848 price tag; with the most expensive listed at a staggering US$196,875. (AFP)