Frustrated by continuing violence in Kabul, the United States is in the midst of one of its most aggressive attempts to link Pakistan with the militant Haqqani network and convince Pakistan’s military to confront the group believed to have a safehaven within Pakistan’s tribal areas.

The latest push by the U.S. was delivered by Chairman of the Joint Chiefs of Staff Adm. Mike Mullen to Pakistani army chief Gen. Ashfaq Parvez Kayani.

In a two hour, one-on-one meeting this weekend, Mullen “conveyed his deep concerns about the increasing — and increasingly brazen — activities of the Haqqani network and restated his strong desire to see the Pakistani military take action against them and their safe havens in North Waziristan,” according to his spokesman, Capt. John Kirby.

The Pakistani military did not immediately respond to a request to comment. But before the meeting, Kayani told Reuters, “Relations are good. They are improving.”

In Kabul, U.S. military and civilian officials express a level of frustration with Pakistan that is more overt and public.

Officials use phrases like “the gloves will come off” and the relationship has “turned a corner,” although they don’t seem to know – or have any unity on -what steps will come next.

The officials are responding to two major attacks in the last week: the 20-hour siege in Kabul that included six rockets landing inside the U.S. embassy, and a massive truck bomb outside of Kabul that injured 77 NATO service members – the single largest number of U.S. casualties in any incident in 10 years of war.

U.S. officials blamed both incidents on the Haqqani network, which is believed to operate out of North Waziristan.

The most pointed critique came from the U.S. ambassador to Pakistan, who accused the Pakistani government of having direct ties with the Haqqani network. His assertion was one of the most aggressive statements made in years by a U.S. diplomat serving in Islamabad.

“There is evidence linking the Haqqani Network to the Pakistan government,” Cameron Munter told Radio Pakistan, a state-run news agency, in a remarkably frank comment that “accurately reflected the ambassador’s mood,” according to a U.S. official. “We have to make sure that the efforts that we are making to build the ties between our intelligence services bring about results,” Munter continued. “We cannot let events like that happened in Kabul to take place.”

Munter’s pointed criticism is rare coming from a Pakistan-based diplomat, but it was just one of many examples of the U.S. piling pressure on Pakistan since the siege in Kabul.

On Wednesday,  Secretary of Defense Leon Panetta said, “Time and again we’ve urged the Pakistanis to exercise their influence over these kinds of attacks from the Haqqanis, and we have made very little progress in that area… I’m not going to talk about how we’re going to respond,” he continued. “We’re not going to allow these types of attacks to go on.” His comments were echoed by U.S. ambassador to Afghanistan Ryan Crocker, the top U.S. commander in Afghanistan, Gen. John Allen, and Vice President Joe Biden.

And now, according to one Western official, U.S. officials are even looking for evidence that directly links the Haqqani network with Pakistan’s premiere intelligence service, the ISI, – a development first reported by the Wall Street Journal.

U.S. officials are also particularly intrigued by the timing of an interview given by the day-to-day commander of the Haqqani network, Sirajuddin Haqqani, to Reuters.

Just hours after Kayani met with Mullen, Haqqani told Reuters that he was in Afghanistan, not Pakistan. Haqqani also told Reuters, in a slight shift in his rhetoric, that he was willing to consider negotiations with the United States if the leader of the Taliban, Mullah Omar, begins negotiations – an apparent attempt to link himself directly with fellow Afghan insurgents.

The tensions between the militaries and the intelligence services extend to the two governments. This weekend, Pakistani Prime Minister called off his visit to New York for the United Nations General Assembly after, according to a Pakistani official, the White House refused a request for a bilateral meeting with President Obama.

Officially, Yusuf Raza Gilani said he needed to stay in Islamabad to coordinate relief for floods that have killed more than 200 people. The U.N. says it needs $365 million to help more than 5 million people who have been affected.