The United Nations has launched a $22m (£12.5m) appeal in aid of Guatemalan survivors of floods and landslides caused by Tropical Storm Stan.
More than 650 people in Guatemala are confirmed dead, while hundreds more people are thought to be missing in the aftermath of the storm.
At least 100 people have died elsewhere in Central America and in Mexico.
The UN said that providing food, water, shelter and sanitation are the priorities for international aid.
Guatemalan President Oscar Berger has said 130,000 people have been directly affected by the storm.
Over 90,000 people are still living in government shelters.
Officials in Guatemala are calling for a number of remote communities to be declared mass graves, after they were engulfed by landslides.
Rescue efforts were suspended in some areas on Sunday after it was deemed too dangerous to dig for survivors.
Stan slammed ashore as a category one hurricane in southern Mexico on Tuesday. It quickly lost force, but most of the damage has been done by torrential rains lasting days on end.
Army and civil defence workers reached some remote communities including the western township of Tacana, near the Mexican border, on Sunday.
But Guatemalan Vice-President Eduardo Stein said rescuers had still not been able to reach at least 90 villages cut off by mudslides.
Some estimates said as many as 1,400 people were feared buried.
Two Mayan villages in the worst affected area have been completely submerged by a slick of mud.
'Worse than Mitch'
Diego Esquina, the mayor of Panabaj, said his village "will no longer exist".
"We are asking that it be declared a cemetery. We are tired, we no longer know where to dig," he said.
"The bodies are so rotten that they can no longer be identified. They will only bring disease."
Some 77 bodies have been recovered from Panabaj, but about 250 are still missing, the mayor said.
Nearby Tzanchaj was similarly devastated.
"Entire families have disappeared," local official Diego Sojuel told the Associated Press news agency.
Taxi driver Gaspar Taxachoy returned from working in Guatemala City to discover his home buried in mud.
The bodies of his wife, two daughters and a son have been found. "I'm only missing one more son," he told AP.
The BBC's Claire Marshall, in Mexico, says it is the region's poorest people who have been worst hit, with precariously-built hillside communities drowned by the mudslides.
Colombia and the US have said they will send food, blankets and first aid equipment to help victims in Central America and Mexico.
After Guatemala, El Salvador has suffered greatest loss of life, with at least 71 confirmed deaths.