US President Donald Trump sings national anthem to mixed reception

US President Donald Trump was greeted with a mixed reception from a college football crowd in Atlanta as he took to the field for the national anthem.

Months after courting controversy by criticising NFL players who kneel during the anthem to protest racial injustice, as well as the league itself for allowing it, the president got his chance to show support for the anthem.

After ROTC members escorted him onto the field, Trump sang the anthem with his hand over his heart and an American flag pin on his lapel, though many took to social media afterwards suggesting that the president appeared to have forgotten some of the words.

Earlier, when giving a speech in Nashville, Tennessee, Trump had said: "We want our flag respected and we want our national anthem respected also."

As he took the field before Alabama and Georgia faced off in the College Football Playoff National Championship, the president was greeted by the tens of thousands in Atlanta with cheers and a smattering of boos.

He then watched the game from a private box overlooking the Alabama sideline, before departing the stadium during half-time, as Georgia led Alabama 13-0.

Alabama ultimately came back to win a thriller in overtime, 26-23. Freshman quarterback Tua Tagovailoa replaced an ineffective Jalen Hurts to start the second half and threw for 166 yards and three touchdowns in a stunning win.