Gen. David Petraeus, commander of U.S. Central Command, has told U.S. officials the next two weeks are critical to determining whether the Pakistani government will survive, FOX News has learned.

"The Pakistanis have run out of excuses" and are "finally getting serious" about combating the threat from Taliban and Al Qaeda extremists operating out of Northwest Pakistan, the general added.

But Petraeus also said wearily that "we've heard it all before" from the Pakistanis and he is looking to see concrete action by the government to destroy the Taliban in the next two weeks before determining the United States' next course of action, which is presently set on propping up the Pakistani government and military with counterinsurgency training and foreign aid. 

Petraeus made these assessment in talks with lawmakers and Obama administration officials this week, according to individuals familiar with the discussions.

They said Petraeus and senior administration officials believe the Pakistani army, led by Chief of Staff Gen. Ashfaq Kayani, is "superior" to the civilian government, led by President Ali Zardari, and could conceivably survive even if Zardari's government falls to the Taliban. 

American officials have watched with anxiety as Taliban fighters advanced earlier this month to within 70 miles of the capital city of Islamabad. In recent days, the Pakistani army has sought to reverse that tide, retaking control over strategic points in the district of Buner even as the Taliban struck back by kidnapping scores of police and paramilitary troops. 

The see-saw nature of the battles Wednesday demonstrated to U.S. officials that, as one put it to FOX News, "even with intent and superior technology, the capability may not be there" for the Pakistani army to defeat the extremists.

As for the security of the Pakistani nuclear arsenal, Secretary of State Hillary Clinton said last Saturday, in an interview with FOX News in Baghdad, that the U.S. believes the arsenal to be "safe" but only "given the current configuration of power in Pakistan." 

She described as "the unthinkable" a situation in which the the Zardari government were to be toppled by the Taliban, adding "then they would have the keys to the nuclear arsenal of Pakistan, and we can't even contemplate that. We cannot let this go on any further..."

The officials who spoke with Petraeus, however, said he and they believe that even were Zardari's government to fall, it was still conceivable that Kayani's army could maintain control over the nuclear arsenal. 

That is because the Pakistani arsenal is set up in such a way -- with the weapons stockpile and activation mechanisms separated -- so as to prevent easy access by invaders. Moreover, the Taliban is not believed at present to possess the sophisticated technical expertise necessary to exercise full "command and control" over a nuclear arsenal, and would probably require weeks if not months to develop it.

The anxiety with which U.S. officials are monitoring events in Pakistan is compounded by a battle here at home over how best to help the Pakistanis. Some members of Congress want to attach benchmarks to any aid provided to Islamabad -- a move opposed by the Obama administration -- while still others wish to transfer authority over key funding streams from the Defense Department to the State Department, also opposed by the administration.

At a House Armed Services Committee hearing on Wednesday, Chairman Ike Skelton,D-Mo. asserted that the existing funding mechanism, the Coalition Support Initiative, under which the U.S. reimburses Pakistan for military expenditures undertaken in support of the U.S. global war on terror, "is not serving the interests of either our country or Pakistan very well." 

Michele Flournoy, U.S. under secretary of defense for policy, rejected that view, saying the initiative has proved "absolutely critical" to the missions in both Pakistan and Afghanistan.

At the same hearing, Assistant Secretary of State Richard Boucher, whose bureau oversees South and Central Asia, told lawmakers the Obama administration favors the Defense Department retaining control over the new funding mechanism for Pakistan being proposed, a Title X provision entitled the Pakistan Counterinsurgency Capabilities Fund (PCCF). 

The goal of PCCF is to provide funding for the immediate training and equipping of the Pakistani army to fight a counterinsurgency war against the Taliban and al-Qaeda. The Pakistani army, U.S. officials say, has historically been modeled to fight a conventional war against India, as opposed to unconventional warfare against non-state actors like terrorist groups.

A final problem, officials told FOX News, was that no one in the U.S. possesses "an understanding of the Taliban's true objective." It remains unclear to policymakers here whether the group truly seeks to overthrow the Zardari government or merely to carve out a territory within Pakistan in which it can establish safe haven, impose Sharia law, and plot attacks on external targets.