KABUL — July 2009 has become the deadliest month for foreign troops fighting an eight-year war in Afghanistan, as Taliban guerrillas hone bombing techniques and Westerners struggle in the harsh climate.

A month before Afghanistan goes to the polls for the second time to elect a head of state, British and US troops are pressing some of the biggest assaults of the war by storming Taliban bases in previously no-go southern areas.

The US military has spoken about of pockets of resistance but officials say the British, whose apparent equipment shortages have sparked huge debate in Britain, have encountered some of the deadliest combat.

The independent website icasualties.org, which calculates military losses in Afghanistan and Iraq, put the number of dead in the Afghan war at 47 so far this July, topping the previous records of 46 in both June and August 2008.

In less than seven months, 203 foreign troops have died in Afghanistan, compared with 294 in the whole of 2008, 232 in 2007 and 191 in 2006.

Just 12 soldiers died in 2001, when US-led troops invaded at the start of the "war on terror".

The top US commander recognised that Taliban militants were now more violent and better organised, warning that troops faced a crucial 18-month battle to help stabilise Afghanistan.

Admiral Michael Mullen, chairman of the Joint Chiefs of Staff, said the latest operations in southern province Helmand were only "just beginning", in an interview with the BBC's Arabic TV service.

"I know it's (security's) got progressively worse over the three, three-and-a-half years since 2006," he said at Bagram Airbase outside Kabul.

"And the Taliban has got much better. They are much more violent, they are much more organised and so there's going to be fighting that is associated with it," said Mullen.

Although he expressed confidence that there were sufficient resources in Helmand to hold areas taken by troops from the militants, the head of the British Army, General Richard Dannatt has called for more troops on the ground.

"I don't mind whether the feet in those boots are British, American or Afghan, but we need more to have the persistent effect to give the people confidence in us. That is the top line and the bottom line," he said.

The operations in the south are the first major test of US President Barack Obama's sweeping new stratgey to stabilise Afghanistan, which ordered 21,000 extra troops to deploy.

About 4,000 US Marines, backed by hundreds of Afghan forces, were dropped behind Taliban lines on July 2. About 3,000 British troops have been pressing Operation Panther's Claw slightly further north since June 23.

Makeshift bombs, known in military parlance as improvised explosive devices (IEDs) have also become increasingly sophisticated, and the cause of death of about 80 percent of soldiers killed in the Afghan insurgency, officials say.

"On flat land as in Helmand, the Taliban can't fight troops face to face. IEDs are the best weapon for a guerrilla on such terrain. They can strike troops by IED and block their movement," said Afghan analyst Waheed Mujda.

"Once their routes are blocked, they have to pass through less flat terrain. There they (the Taliban) can attack them directly," he said.

Although US commanders claim their military is the best counter-insurgency force in the world after six years in Iraq, conventional fighting machines have for years been laid low by guerrillas. Heat can also slow down foreigners.

"In a guerrilla war, a soldier must have the capability to manoeuvre. In Helmand, most NATO or US soldiers lack that capability, due to the harsh climate and weight of their gear," Mujda added.

Scorching summer temperatures can reach up to 46 degrees Celsius (115 degrees Fahrenheit) in Helmand.

Britain has lost 15 soldiers this month. Eight were killed in one 24-hour period and the death of a lieutenant colonel marked the most senior British Army officer killed in action since the 1982 Falklands War.

"The terrain is more difficult for the British than the Americans. Where they are in the north, there are a lot of canals, few roads and a lot of IEDs, which limit their movement," said one Western military official.

"It seems that the insurgents have decided to stay and defend northern Helmand, while they have fled or stopped fighting in the south," said one US officer on condition of anonymity.

"We are going to continue to see big losses in the next one or two months," he added. "But once this operation is done, we will have managed to stabilise these areas for the better," he said.