Up to 100 police officers are being deployed from Scotland to London to assist with the Extinction Rebellion protests.
The public order officers will work with colleagues in the Metropolitan Police responding to the climate change demonstrations.
They will be deployed from early next week after Police Scotland Chief Constable Iain Livingstone approved the request from the National Police Co-ordination Centre on behalf of the Met.
Met Police chief Cressida Dick said on Friday the force has been "stretched" by the protests, impeding its ability to respond to other crimes.
Demonstrations in London have seen more than 1,200 arrests.
Mr Livingstone, who has briefed Scotland's Justice Secretary on the move, said it would not undermine Police Scotland's ability to protect the public in Scotland.
He said: "I have agreed to send a number of officers for a short time to assist with the policing of the Extinction Rebellion protests currently taking place in the city.
"The Scottish Police Federation is engaged in this process and the safety and welfare of my officers and colleagues is paramount.
"Scotland has benefited from mutual aid in the past and will do so again in the future. It's therefore appropriate that, as the UK's second biggest police service, we supply officers when asked to do so by other forces."
Activists blocked the entrance to the BBC's central London headquarters on Friday, with some scaling the front of the building.
On Thursday, demonstrations focused on London City Airport, where protesters attempted a "Hong Kong-style occupation" of the terminal building, with hundreds blocking the main entrance.
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