WASHINGTON - Tens of thousands of people lined the streets of downtown Washington DC early on Wednesday morning to catch a glimpse of Pope Francis, who is making his first ever visit to the United States.

Though security in the area was tight - with all those gathered forced to go through metal detectors - the scene still took on a carnival atmosphere.

Vendors selling Pope T-shirts, caps, posters and flags were doing a brisk business, as were those peddling ice-cream and water.

With most of the crowd waiting for hours in the sun for the papal parade to begin, many kept themselves entertained either by chanting or singing songs.

Ms Ingrid Vaca, 51, a cleaner, waited by the street overnight to get a choice spot for the Parade. She said was hoping to be blessed by Pope Francis and also wanted him to speak to US President Barack Obama about the plight of immigrants.

Retiree Linda Franklin, 66, said she was up till late making a poster but still got in position by 5.30am.

"This is a once in a lifetime opportunity and I feel so blessed to have gotten so close to the Pope."

During the parade, the Pope made an unplanned stop as he blessed a baby picked out of the crowd by Vatican security.

Before the parade, Pope Francis met US President Barack Obama at the White House. In a rare English speech, he praised Mr Obama for his efforts to combat climate change and stressed that more needs to be done to tackle the problem.