A lake near the northern Pakistani town of Aliabad is on the verge of breaking its banks and displacing thousands of people, officials have warned.
They say that if Attabad lake does flood, at least 36 villages could be submerged along with crops.
The lake formed when landslides blocked a river in January. The trapped water is now at dangerously high levels.
Officials say that parts of the famous Karakoram highway to China could be washed away if the lake's banks burst.
They told an emergency news conference on Tuesday that the danger will be highest during the rainy season in June.
The landslide at the village of Attabad, about 30km (18 miles) north-east of Aliabad, occurred during snowstorms in January.
The area where the landslide took place is remote
The BBC's M Ilyas Khan in Islambad says it cut off part of the Karakoram highway - which has remained closed to traffic and is not expected to be operational again for many years.
The landslide caused debris to block the River Hunza, which in turn prevented water from flowing downstream and created what is now referred to as Attabad lake.
Over the last four months water has been accumulating in the lake, which is now about 11km (6.8 miles) long. The water is more than 330ft (100m) deep in places.
Officials believe that by the first week of June the water will start overflowing the debris that is blocking its passage.
So far, more than 3,000 people have been displaced by the rising water levels upstream of Attabad.
Most belong to two villages that were submerged in late March and early April.
Another 1,000 locals are expected to leave their homes in a week or so when water will overrun low-lying areas of Gulmeet town, located on the northernmost limits of Hunza valley.
Officials warn that once the blockage is breached, rushing waters may submerge villages downstream of Attabad, displacing as many as 20,000 people.
Our correspondent says that a recurrent theme has been the indifferent attitude of the authorities.
The military-run National Disaster Management Authority (NDMA) announced soon after the landslide that it would deploy the army's engineering wing, the Frontier Works Organisation (FWO), to cut a breach in the debris which would allow water levels to recede.
It said at the time that the work would be completed in three weeks. But the FWO took more than three weeks to arrive at the scene.
In February, the NDMA said it would start releasing water from the lake by 15 March. Officials later said they would finish the job by the end of April.
The FWO now claims they have excavated some 30m of the debris, but some locals say they have only removed half of what they claim.