KABUL - US General David Petraeus formally took up his new role as commander of the Afghan war during a ceremony at NATO headquarters in Kabul on Sunday, saying: "We are in this to win."

In a solemn ceremony held amid tight security, Petraeus received the colours of US and NATO forces engaged in the Afghan war, marking his assumption of command over the 140,000 foreign troops in Afghanistan.

Wearing fatigues, he told a small crowd of Afghan military, civilian VIPs and diplomats, the war had reached a "critical moment" and reiterated his call for a united effort against the Taliban-led insurgency in the country.

"We are engaged in a battle of wills," he said.

"We must demonstrate to the people of Afghanistan and the Taliban that... NATO forces are here to safeguard the Afghan people and we are in this to win. That is our objective.

"We have arrived at a critical moment. We must demonstrate to Al-Qaeda and its network of extremist allies that they will not be allowed to establish safe havens in Afghanistan from which they can launch attacks," he said.

Petraeus arrived in Kabul on Friday to take over NATO`s 47-nation International Security Assistance Force (ISAF) from US General Stanley McChrystal, sacked last month by President Barack Obama for insubordination.

He paid tribute to McChrystal, who served for almost a year, saying: "No one did more in getting the inputs right than Stan McChrystal.

The four-star general made his public debut on Saturday as commander of foreign forces in Afghanistan, at a US embassy reception to mark the Fourth of July American Independence Day.

He later met Afghan President Hamid Karzai, telling him "that I applaud his commitment to inclusivity, transparency, integrity and accountability."

The president`s office said they discussed corruption concerns after billions of dollars in US aid was blocked last week following a report that cash for development projects was being shipped out on commercial flights.

Karzai rejected the graft allegations as "baseless," his office said, yet added that both he and Petraeus agreed "anti-corruption was the main part of the war against terrorism and emphasised cooperation to reduce it".

Observers have said Petraeus faces a tricky task to bring peace and secure a face-saving exit for allied troops fighting the Taliban.

He arrives as the deaths of US and NATO soldiers are touching record highs in intensified fighting, along with questions about the wisdom of committing huge resources in manpower and money to what could yet be a lost cause.

His appointment as commander in Afghanistan has been welcomed by local officials, including Karzai, who is increasingly seen in the West as a loose cannon.

"The biggest challenge for David Petraeus is the Afghan government and president Karzai himself," said political analyst Haroun Mir.

Analysts have also urged Petraeus to make immediate adjustments to turn around rapidly a war seen as bogged down to the Taliban`s advantage.

Despite assurances from Obama -- reiterated Sunday by Petraeus -- that the change of command does not mean a change in strategy, the general has already hinted some tweaks could be in the air.

Troops have complained that McChrystal`s "courageous restraint" rule, aimed at minimising civilian casualties, prevents them from properly defending themselves -- thus contributing to the spike in casualties.

A total of 102 foreign soldiers died in June, almost triple the May toll and far outstripping the previous highest monthly figure of 77 in August.

So far in 2010, more than 320 troops have died, compared with 520 for 2009.

Nine more NATO soldiers were wounded by overnight mortar attacks on a base in the eastern province of Kunar, said a military statement Sunday.

Afghan authorities said Sunday they killed more than 60 rebels in raids against militants and drug gangs in restive southern Helmand province.

More than 16 tonnes of drugs, mainly opium, were also seized in Bahramcha district, the interior ministry said.

In the volatile Musa Qala district of Helmand, four civilians were killed and five other injured in two incidents involving remote-controlled bombs, regional authorities said.

A bomb placed on donkey exploded and another on a motorcycle were detonated in a busy bazaar on Sunday morning, the provincial governor`s office said in a statement.

BDST: 20.45 HRS, July 4, 2010