It is an agreement that will be made permanent in January when the transfer window re-opens.
The deadline for pushing loan deals through in England is Thursday, Rovers hope to have everything in place by then so the move can go smoothly.
20 year old King went out with the United squad to Turkey and he has also been impressing at international level with Norway.
He was given a part to play in the Champions League game, but Fergie is believed to be mulling over letting the youngster go.
Rovers are prepared to offer him first team football and if this comes off there could be more deals to be had with United.