Kyle Dempster and Scott Adamson have been missing for a week after their latest attempt to climb the notoriously difficult 23,000ft peak

The Pakistani military has set up a helicopter search for a pair of American climbers missing for more than a week after an attempt to climb the notorious Ogre II mountain.

Days of snowy and cloudy conditions had left rescuers unable to reach the remote peak to search for renowned alpinists Kyle Dempster and Scott Adamson, said Jonathan Thesenga, of Black Diamond Equipment.

But a break in the weather meant he Pakistan military helicopters were due to begin the search on Saturday morning local time. An organization called Global Rescue also has helicopters and a medivac aircraft on standby.

Facebook Twitter Pinterest Kyle Dempster, along with Scott Adamson, made an attempt to climb the same mountain last year. Photograph: Nathan Smith/AP

Dempster and Adamson, who are from Utah, were due back at base camp on 26 August after leaving five days earlier to begin their ascent up the north face of the 22,864ft (6,969m) Ogre II in the Panmah Muztagh subrange of the Karakoram mountains.

Bad weather had hindered rescue efforts since Sunday , which began on Sunday, Thesenga said. Four guides had been dispatched to search the mountain on foot.

Planetmountain (@Planetmountain) Funding appeal for Scott Adamson & Kyle Dempster missing on Ogre 2, Pakistan #alpinism https://t.co/id3eKsyZ2C pic.twitter.com/0LRbpAZTGZ

Climbing Mag (@ClimbingMag) Kyle Dempster and Scott Adamson Missing on Pakistan's Ogre 2 https://t.co/DoG8jK1Hvf #climbing #rockclimbing pic.twitter.com/Xbpwz3SV1d

Dempster, 33, and Adamson, 34, are two of the most accomplished alpinists of their generation, Thesenga said. The pair made the same attempt last year, when Dempster broke his leg after a 100ft fall and the two then fell 400ft while trying to get down the mountain.

Six other climbers, including two from the US, were at base camp on the mountain and ready to ascend if they were needed to help, he said.

“They have built their careers on cutting-edge alpine ascents from Pakistan to Alaska,” Thesenga said. “We remain optimistic that they are going to get out of the mountains and have this amazing story of survival to share.”

The Ogre massif, also known as Baintha Brakk, is regarded as one of the most difficult climbs in the world thanks to its steep, rocky faces. Doug Scott, the legendary British climber, broke both legs on the first ever ascent of the Ogre in 1977 and it was not climbed again until 2001.