Defense Secretary Leon Panetta on Wednesday warned the United States would retaliate against insurgents based in Pakistan blamed for staging a dramatic attack in the Afghan capital.

A day after a 19-hour assault staged near the US embassy and NATO headquarters, Panetta expressed frustration that the Pakistani government has so far failed to crack down on Haqqani network militants that Washington suspects carried out Tuesday's attack.

"Time and again we've urged the Pakistanis to exercise their influence over these kinds of attacks from the Haqqanis and we've made very little progress in that area," Panetta told reporters aboard his plane before landing in San Francisco.

"I'm not going to talk about how we're going to respond. I'll just let you know that we're not going to allow these kinds of attacks to go on," he said.

Panetta's tough words come amid strained relations with Islamabad following the US raid that killed Osama bin Laden at his Pakistani hideout on May 2, a raid that Panetta oversaw while he was CIA director.

Islamabad's leaders had no advance word of the secret operation, which has caused anger and soul-searching in Pakistan.

As head of the Central Intelligence Agency, Panetta also presided over a dramatic expansion in drone bombing raids in Pakistan, with robotic aircraft targeting Al-Qaeda and Taliban militants in the country's northwest tribal areas.

US officials have for years demanded Islamabad move against the Haqqani network, which operates in part out of sanctuaries inside Pakistan's borders.

Before the Kabul attack, the US military blamed the Haqqani militants for a truck bombing on Saturday against a NATO base in Wardak province that wounded 77 American troops.

"I'm very concerned about the Haqqani attacks because, number one, they're killing people, they're killing our forces.

"But number two, they escape back into what is a safe haven in Pakistan. And that's unacceptable. So the message they need to know is that we're going to do everything we can to defend our forces."

The 19-hour Taliban assault on Kabul turned the city's most heavily secured district into a battle zone. Fifteen people were killed and six foreign troops wounded in the attack.

The insurgents managed to occupy a high-rise building site that towers over the US embassy and NATO's headquarters in Afghanistan, firing rockets and spraying gunfire well inside a supposedly secure zone.

The bold assault is the latest in a series of attacks in Kabul that suggest the Taliban can move with apparent ease around the capital, a decade after their regime was ousted by US-led forces.

The violence raised questions about the Western-backed government's security forces, which are supposed to gradually take over responsibility from the NATO-led mission.

But Panetta said while the attack inside Kabul provided grounds for concern, the Afghan security forces performed well.

"I think generally the response was good," Panetta said. The Afghans responded "quickly" and "casualties were limited."

"Basically they were able to defeat their effort," Panetta said.

The assault occurred as the Pentagon chief was holding a video conference with the US and NATO commander in Afghanistan, General John Allen, who had to break away several times to get updates on the attack, Panetta said.

Despite Tuesday's attack, the defense secretary said the Taliban-led insurgency has lost ground and could no longer directly confront NATO troops.

He said he shared the US commander's view that "these kinds of attacks, sporadic attacks and assassination attempts are more of a reflection of the fact that they're losing their ability to be able to attack our forces on a broader scale."

Panetta flew to San Francisco for an annual meeting of the US-Australia alliance, attended by foreign and defense ministers from each country.

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