Summit talks productive says Obama

The trilateral leaders' summit comes amid continued violence in the region, with the White House seeking a commitment from both governments to step up their efforts against the Taliban.

Speaking shortly after the meeting, Mr Obama pledged "lasting commitment" to the democratic government of both countries, adding: "The security of Pakistan, Afghanistan and the United States are linked."

The threat of insurgency further destabilising Pakistan was underlined on Wednesday as fighting continued in the Swat Valley.

Security forces said they killed dozens of Taliban fighters in the region through heavy mortaring of the militants' strongholds.

Meanwhile, civilians continued to flee the area to escape the violence. The government in Islamabad said it believes those left homeless by the situation could reach 500,000.

It follows the breakdown of a three-month ceasefire.

In Washington, Mr Obama - flanked by Mr Zardari and Mr Karzai - said that the US, Pakistan and Afghanistan must co-operate in fighting insurgents who control parts of the Pakistan-Afghanistan border and "deny them the space" to threaten local citizens. He added that both Mr Zardari and Mr Karzai recognised the seriousness of the threat.

In his remarks following the summit, Mr Obama did not mention the Taliban once by name, instead speaking of the threat from al Qaida and its "extremist allies". He said the three nations represented at the talks had a common goal in wanting to "disrupt, dismantle and defeat" terrorists and militant insurgents in the region.

The US president called on the two visiting heads of states to share intelligence and co-ordinate efforts to "isolate, target and take out" insurgents. In return he vowed US support and money to build schools, roads and hospitals in a bid to win hearts and minds.