Selfie sticks are becoming a must-have for tourists globally but Washington's top museums have banned the photography accessory.

"This is a preventive measure to protect visitors and objects, especially during crowded conditions," The Smithsonian, the largest research and museum group in the world, said in a statement.

The selfie stick allows you a longer reach when using a smartphone or camera to take a picture of yourself.

"We encourage museum visitors to take selfies and share their experiences and leave the selfie sticks in their bags," the Smithsonian said. The new rule is the first change in years to the Smithsonian's rules. "I can't think of any recent change that's been similar to this," spokesman John Gibbons said.

"I don't think 10 years ago that you could have predicted there would even be such a thing, let alone that it would be so popular."

The Smithsonian consists of 19 museums and galleries in the US capital, the National Zoological Park and nine research centres. It had more than 28 million visits last year.