Security in Houston is tight ahead of Sunday's (Monday AEDT) Super Bowl 51, though officials have vowed to support peaceful demonstrations against US President Donald Trump's executive order restricting entry to the US for travellers from some Muslim-majority nations.
The approach by state, regional and federal US security officials reflects a delicate balancing act as more than one million spectators are expected to flood into the Texan city as the New England Patriots take on the Atlanta Falcons.
Protests against Trump's executive order on immigration have spread across the United States, including one last weekend in downtown Houston near where the National Football League has placed many pre-game activities.
Protests are expected to continue throughout the week and into the weekend, even at the game itself. Halftime performer Lady Gaga has been an outspoken critic of Trump.
Amid the protests, officials said no credible threats to the city have emerged ahead of the game, which is expected to be watched by more than 100 million people around the globe.
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All members of the more-than 5,000-officer Houston Police Department will be on patrol alongside regional and federal law enforcement, officials said.
"We have taken every possible precaution to keep people safe," said Houston Mayor Sylvester Turner.
Turner, who asked Trump in a series of posts on Twitter last weekend to rescind his immigration order, said he respected the rights of protesters and would support them so long as they remained peaceful.
"Violence is not going to be tolerated or allowed," he said.
Metal detectors, bomb-sniffing dogs and myriad other security equipment have been deployed across downtown Houston and 7 miles (11 km) southwest at NRG Stadium, which will host the football game.
