US President George W Bush has appealed to the presidents of Pakistan and Afghanistan to put aside their differences and fight terrorism.
Mr Bush hosted a dinner for Pervez Musharraf and Hamid Karzai. But at a public appearance with him, the two leaders did not speak or shake hands.
The two disagree on how to fight the Taleban in their border region.
Gen Musharraf has angrily rejected allegations that his ISI intelligence service aided al-Qaeda and the Taleban.
A document prepared by an official in the Defence Academy, a thinktank linked to the UK Ministry of Defence, said the ISI indirectly backed terrorism by supporting religious groups in Pakistan.
But in a BBC TV interview, Gen Musharraf said his intelligence services were doing an "excellent job" in tracking down and apprehending militants, and that he rejected "200%" calls to dismantle them.
The MoD said the allegations in no way represented its views or those of the British government.
However, Gen Musharraf said he would bring up the matter in discussions with UK Prime Minister Tony Blair at a meeting in London on Thursday.
Feud goes on
At the Washington dinner, the three leaders sat down together and ate soup, sea bass and salad.
A brief White House statement after the meal said the three leaders had agreed to "moderation and defeating extremism through greater intelligence sharing, [and] coordinated action against terrorists".
But there were was no public sign that the feuding between the Pakistani and Afghan leaders is over, says the BBC's Justin Webb in Washington.
Earlier both men stood stiffly beside Mr Bush as he praised them as his "personal friends".
Mr Karzai accuses Pakistan of not doing enough to fight militants, criticism that Gen Musharraf strongly rejects.
The US has become increasingly impatient about the spats, our correspondent says.
Washington is particularly concerned about Gen Musharraf - he adds - who has cut a strange figure during his visit.
The Pakistani leader has said some things while plugging his new autobiography which have raised a few eyebrows among Americans, he says, even suggesting he was considering war with the US after the 11 September 2001 attacks.
It is nearly five years since the Taleban were forced from power, but thousands of international troops remain in the country hunting Taleban supporters, who have regrouped.
Violence and fighting have been increasing, particularly in the south of the country.
The Afghan and Pakistani leaders have been apart on the issue of security in recent months.
President Karzai has suggested that Pakistan has turned a blind eye to Taleban supporters using parts of the country to train and launch attacks on Afghanistan, and accuses Pakistan of sheltering former Taleban leaders.
He has also criticised a peace deal between the Pakistani army and tribal elders in the North Waziristan border region, saying that violence in Afghanistan has increased since the deal.
Gen Musharraf says the deal was necessary to fight the Taleban and strongly rejects Mr Karzai's allegations. He says Pakistan is doing all it can to fight terrorism and, in turn, accuses Mr Karzai of inaction.