The Japanese climbers Ryuseki Hiraoka and Atsushi Taguchi were attempting to summit the 7,027-metre (23,054-foot) Spantik mountain in the Karakoram range before they went missing.
"The rescuers saw the climbers and recognised them by their clothes, but they could not determine their condition," Naiknam Karim, the CEO of Adventure Tours Pakistan (ATP) which organised the tour, told AFP.
The two were spotted during a military helicopter search on Thursday that was called off due to poor weather conditions.
"There has been no communication between the two Japanese climbers and officials at basecamp since they started their expedition," Karim earlier said.
"They were seen on June 10 (for the) last time at above 5,000 metres."
Another team of Japanese climbers raised the alarm on Tuesday after arriving at Camp 2, at around 5,650 metres, where Hiraoka and Taguchi were scheduled to be.
The search is scheduled to resume on Friday. "An 8-member rescue team including five Japanese climbers will ascent on foot and search for them," Karim Added.
The pair had reached base camp on June 3 and were attempting the climb without the help of porters.
Spantik, also known as the Golden Peak, is described as a "relatively accessible and straightforward peak" on the website of a separate tourist company, Adventure Tours.
The country is home to five of the world's 14 mountains higher than 8,000 metres -- including K2, the world's second highest.
More than 8,900 foreigners visited the remote Gilgit-Baltistan region in 2023, according to official figures from the government, where the summer climbing season runs from early June to late August.