Up to 100 civilians, including women and children, are reported to have been killed in Afghanistan in potentially the single deadliest US airstrike since 2001. The news overshadowed a crucial first summit between the Afghan President and Barack Obama in Washington yesterday.

President Obama, after White House meetings with President Karzai of Afghanistan and Asif Ali Zardari, the Pakistani President, pledged “every effort to avoid civilian casualties” in the war against the extremists.

His comments followed the expression of deep regret by Hillary Clinton, the US Secretary of State, during an earlier appearance with Mr Karzai in Washington.

News of the airstrikes came as Mr Obama met Mr Karzai and Mr Zardari for a trilateral summit aimed at pressing both leaders to join forces in confronting al-Qaeda and the Taleban. Mr Karzai had travelled to Washington to meet an Obama Administration that has little faith in his ability to take on the Taleban, the massive opium trade funding it, or rampant corruption.

Despite the Afghan leader’s pre-summit vow to make the airstrikes a focus of his meeting with Mr Obama, a top aide to the US President said that Mr Karzai was given a clear message in the Oval Office that he had to do more to clamp down on the bribes and influence-peddling that is poisoning Afghan governance.

General Jim Jones, Mr Obama’s National Security Adviser, told reporters after the White House meeting that Mr Karzai had been told by the US President that he wanted to see “concrete results” towards stamping out corruption in Afghanistan.

After the meeting Mr Obama said that the the session had been extraordinarily productive, adding: “I’m pleased that these two men . . . fully appreciate the seriousness of the threat that we face.” He said that the three countries are co-operating in new ways to fight terrorism and improve the lives of Pakistanis and Afghans.

He warned: “The road ahead will be difficult. There will be more violence and there will be setbacks. But let me be clear. The United States has made a lasting commitment to defeat al-Qaeda but also to support the democratically elected sovereign governments of both Pakistan and Afghanistan. That commitment will not waiver and that support will be sustained.”

Mr Obama has ordered an additional 21,000 troops to Afghanistan this year. One of his greatest struggles is persuading a sceptical US Congress to approve a five-year, $7.5 billion aid package that is aimed at bolstering support for Mr Zardari among the Pakistani people by investing in schools, hospitals and other civilian projects.

Civilian casualties in Afghanistan from multiple airstrikes in the past year have enraged the local population and further undermined Mr Karzai’s ability to tackle the Taleban and al-Qaeda. This week’s airstrikes took place in the Taleban-controlled area of Bala Baluk, in Farah province. US military officials in Kandahar said that the number of fatalities was nearer 30, but the International Committee of the Red Cross (ICRC) said that the death toll was far higher.

Jessica Barry, an ICRC representative, said that an international Red Cross team in Bala Baluk saw “dozens of bodies in each of the two locations” on Tuesday. “There were bodies, there were graves, and there were people burying bodies when we were there,” she said. “We do confirm women and children.”

Many of those killed and injured had taken refuge in the villages to escape the fighting between the Taleban and the Afghan National Army, which had US “trainers” embedded within it. They had the ability to call in the US jets, part of a new command operating outside the auspices of Nato but under a new command known as US for Afghanistan.

The Washington summit was aimed at showcasing Mr Obama’s new strategy of viewing Afghanistan and Pakistan as a linked foreign policy issue.

In essence Mr Obama’s aim is to get the two leaders, whose countries have a deeply troubled relationship beset by mutual suspicion, to co-operate in wiping out al-Qaeda and the Taleban, particularly in the lawless border regions.

As the leaders met events on the ground underscored the enormity of the military and diplomatic task that Mr Obama has before him in the region. As the US airstrikes were condemned in Afghanistan, heavy fighting also continued between the Pakistani Army and Taleban militants who have moved to within 60 miles of the capital, Islamabad. The sudden move by the Pakistani authorities to take the fight to the Taleban was welcomed in Washington, where the parlous political and security situation has become the US Administration’s greatest foreign concern.

“I’m actually quite impressed by the actions that the Pakistani Government is now taking,” Mrs Clinton said.

US officials had been angered by a peace deal in February between Mr Zardari’s Government and the Taleban in the Swat Valley, ceding control of the region to the militants. Since the truce broke down last week thousands of civilians have fled, with Pakistani authorities predicting a refugee crisis that could involve 500,000.

The sobering reality for Mr Obama is that his top foreign policy priority — stabilising Pakistan and Afghanistan — largely rests on working with two leaders who are politically imperilled at home. Although Mr Karzai now seems assured of re-election later this year because his main rivals have dropped out, his writ barely extends beyond the capital, Kabul.

Mr Zardari has seen his popularity plummet at home, but the Obama Administration is still determined to give him more time. Mrs Clinton said: “He inherited a very difficult and unmanageable situation. I think a little more understanding \ on our part about what he confronted.”

In Washington, Mr Zardari said: “My democracy needs attention and needs nurturing. Pakistani democracy will deliver, the terrorists will be defeated by our joint struggle. Me, my friend President Karzai and the United States . . . will stand shoulder to shoulder with the world to fight this cancer and this threat.”

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