MUZAFFARABAD, Pakistan (Reuters) – International efforts to help up to three million survivors of Pakistan”s devastating earthquake are gathering momentum, but time is short and much more is needed, aid officials said on Sunday.

&#34It is very high risk that this population is in,&#34 United Nations Humanitarian coordinator Rashid Khalikov told reporters, estimating rescuers had only five or six weeks to get people under shelter before the harsh Himalayan winter sets in.

&#34Whether we are able to do it in six weeks or not, we will know only six weeks after today, but we will do our best,&#34 he said as the confirmed death toll in northern Pakistan passed 53,000, with more than 75,000 seriously injured.

Those figures are expected to rise substantially, with untold numbers lying buried in the rubble of an estimated 2,000 unreached villages and aid officials fearing a second wave of deaths among the untended injured.

&#34Clearly much more needs to be done,&#34 Khalikov said.

More of the vital helicopters needed to reach otherwise inaccessible mountain villages cut off by landslides were arriving — three British Chinook heavy transporters the latest — and more were due.

India and Pakistan also held out hope that new aid routes could be opened across the line dividing disputed Kashmir, the worst-hit area in the October 8 catastrophe.

India offered to set up three relief centres along the de facto border in Kashmir, over which the nuclear-armed rivals have fought two of their three wars.

Pakistan proposed opening five crossing points to Indian Kashmir, where 1,300 people were killed.

But the two governments, widely accused of putting politics before people, did not appear to be in a great rush to deal with the enormously sensitive issue; Pakistan said it hoped talks could begin by the end of this month.

Aid officials, who have been complaining ever more loudly for days that the world is not doing enough, say time is crucial in a region where winters bring deep snows.

&#34The scarcest commodity at this time is time. All the rest money can buy, but money can”t buy time,&#34 said U.N. coordinator Jan Vandermoortele.

&#34The top priority overall is tents and emergency shelter,&#34 he said. &#34We need helicopters, a lot of helicopters and all types of helicopters.&#34

His colleague Khalikov said the U.N. was pleading for more.

&#34We are talking to all of the countries that have helicopters. We are asking those who have already provided helicopters to allow them to stay longer,&#34 he said.

The Pakistani army is working around the clock to open roads blocked or swept away by landslides when the quake struck, trapping countless survivors in remote valleys and on ridgeline settlements high in the hills.

The road up Pakistan”s Jhelum valley should be re-opened in a week, but it could take six weeks for the nearby Neelum valley, one commander said.

&#34The emphasis is on the need for road engineers. If we can open the roads, that would solve everything,&#34 World Food Programme spokeswoman Mia Turner said, referring to a NATO decision to send an engineering battalion to clear roads.

&#34More than 2,000 villages have to be reached and they have to be reached by roads,&#34 she said as another mule train set off into the hills from a village above the destroyed Pakistani Kashmir capital of Muzaffarabad.

The helicopter aid fleet cannot deliver enough or reach everywhere and pilots report villagers waving flags to signal they needed help, Turner said.

One huge problem is finding enough tents which can stand up to a tough winter and getting them to where they are needed.

An aid official said 540,000 tents were needed but with global supplies limited, there could be a shortage of 200,000 and the U.N. was looking at alternatives.