More than 100 million homes across the United States and millions more worldwide are expected to tune in for the climax of the National Football League season in Houston, which kicks off at 5:30 pm (2330 GMT).

Patriots star Brady will become the first quarterback to win five Super Bowl crowns if he manages to guide his team to victory before a crowd of around 72,000 spectators at the NRG Stadium.

Blanket security will be in place for the game, which takes place at a time of roiling political tensions across the United States following President Donald Trump's controversial immigration order.

Even one of the Super Bowl's traditional sideshows -- the flurry of innovative television advertisements rolled out during the game -- has been caught up in the nation's politically charged atmosphere.

Budweiser beer will show one touching on immigration issues while auto giant Audi's ad will address women's equality.

And in a rare intervention into the bruising world of the NFL, Pope Francis has recorded a video message to be played during the Super Bowl, expressing hope that the occasion can "be a sign of peace, friendship and solidarity for the world."

Trump, who has repeatedly cited his friendship with Brady and Patriots coach Bill Belichick, will not be at the game, but the White House says he will be watching from Florida.

An anti-Trump protest involving around 500 people took place near the Super Bowl venue on Sunday. 

The march, which had been arranged in advance, featured demonstrators bearing anti-Trump slogans, with one that read: "Deport Trump to Outer Space."
                  
- Last laugh for Brady? -                  
                  
A win on Sunday would come 15 years after Brady and Belichick's first Super Bowl triumph in 2002.

It would also represent a satisfying last laugh for Brady following his long-running battle with NFL commissioner Roger Goodell. 

Brady was forced to miss the first four games of the season after losing a legal battle against the league over the 2015 Deflategate scandal, which saw the Patriots superstar accused of cheating by attempting to alter the pressure of balls to his advantage during a key championship game. 

It has led to the prospect of Goodell having to possibly hand over the Vince Lombardi Trophy to Brady and his teammates on Sunday. 

Goodell insists there will be no awkwardness if that should come to pass.

"Tom Brady is one of the all-time greats. He has been for several years," Goodell said, adding it would be an "honor" to hand the Lombardi Trophy to the quarterback.

Brady has done his talking on the field this season. 

He averaged just under 300 passing yards a game in the regular season, and was magnificent in a comprehensive 36-17 demolition of the Pittsburgh Steelers in the AFC Championship game two weeks ago.
                  
- The 'Iceman' cometh? - 

                  
But even Brady's stats pale in comparison with those of his opposite number, Matt Ryan, who received recognition for a stellar season on Saturday after being named the NFL's Most Valuable Player for 2016.

Ryan has led the most potent offense in the league, averaging more than 365 yards a game in the post-season, and just over 300 yards during the regular season. 

Ryan, 31, reached the Super Bowl after four unsuccessful previous playoff appearances. 

Ryan -- nicknamed "Matty Ice" by his teammates -- said the team is comfortable with the burden of expectation. 

"I'm sure everyone will be excited and anxious going into it. But as far as nerves, I feel like we've prepared ourselves for this moment," Ryan said.