NEW YORK - AFGHANISTAN President Hamid Karzai said recent leadership change in Pakistan has offered for the 'first time' a hope of winning the 'war on terror' and called for a joint assault on extremist 'sanctuaries' along their common border.

He also asked the US to provide full backing to the new democratically elected administration of President Asif Ali Zardari, who took over from former military strongman Pervez Musharraf, in fighting extremism.

Relations between the neighbours were strained during Mr Musharraf's rule, with the Afghan leader persistently accusing Islamabad of not doing enough to curb cross-border militancy.

'For the first time, I see in the region a ray of hope,' Mr Karzai said at a New York-based Asia Society forum on the sidelines of the UN General Assembly.

He said Mr Zardari, whose wife former prime minister Benazir Bhutto was killed in a suicide blast, would move away from what he charged was Islamabad's long-standing use of 'radicalism and extremism as an instrument of policy.'

'If we can all work together, Afghanistan, Pakistan, the US and our allies, I see now possibilities of moving beyond the days where one or the other of us may need extremism or radicalism as an instrument of policy and when that happens, there would be no place for extremists to play against all of us and if that happens, there will be no extremist activity as it is now.'

Afghanistan has repeatedly accused Pakistan of clandestinely supporting Taleban rebels, which Washington and Kabul say are using tribal areas in Pakistan along the border with Afghanistan as sanctuaries.

Mr Karzai had also blamed Pakistan's intelligence service for a deadly suicide attack on the Indian embassy in Kabul that killed 60 people - a charge Islamabad has denied.

The Afghan leader said Mr Zardari had a 'very' good understanding of the tribal region and 'the need to change' the situation there.

'My hope is he would have the instruments to (wage the fight against terrorism) ... the instruments means backing from the US, first of all,' he said.

Mr Karzai spoke after Mr Zardari met US President George W. Bush for talks, also at the sidelines of the UN event.

'Pakistan is an ally, and I look forward to deepening our relationship,' Mr Bush told reporters.

The US leader moved to ease Mr Zardari's concerns over unilateral strikes by US forces in Afghanistan on militant hideouts in Pakistan that Islamabad said had caused many civilian casualties.

'And your words have been very strong about Pakistan's sovereign right and sovereign duty to protect your country, and the US wants to help,' Mr Bush said with Mr Zardari by his side.

The Pakistani leader replied, 'We have issues. We've got problems. But we will solve them and we will rise to the occasion.'

Mr Karzai also endorsed a plan voiced by his defense minister for a joint US-Afghan-Pakistani military task force that would be empowered to operate on both sides of the border.

'A force to act together on two sides of the border? A new idea but a welcome idea, I'll back it,' he said to a question.

He also said that any surge in international troops for the war in Afghanistan should be involved in flushing out militants in border 'sanctuaries' in Pakistan instead of penetrating deeper into Afghan villages.

Underlining the need to have a regional approach to fighting terrorism, Mr Karzai said any assault should be 'concentrated on the sanctuaries - on those that train extremists, equip extremists, motivate extremists and then send them across' to Afghanistan.

'The surge, in other words, will work only if you concentrate the deployment of troops at the right places where we need them,' he said. -- AFP