Amid near-open conflict between Pakistan's civilian and military leadership, the Pentagon has neither sought nor received assurances that the Pakistani army won't stage a coup, a Pentagon spokesman said Wednesday.

"This is a matter for Pakistani officials — their government leaders, military and civilian — to work out," the spokesman, Navy Capt. John Kirby, told reporters.

It also is a matter of grave concern in light of Pakistan's status as a nuclear power and the risk that its arsenal — said to be well protected now — could fall into the wrong hands in the event of civil conflict.

The Pentagon disclosed that Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, talked by phone on Tuesday with his Pakistani counterpart, Army Gen. Ashfaq Pervez Kayani. Dempsey's office declined to provide details of the conversation but said it was their first contact since Dec. 21.

Dempsey has an unusually close connection with Kayani. He has known the Pakistani general since 1988, when both attended the U.S. Army's Command and General Staff College at Fort Leavenworth, Kan.

Pakistan's prime minister fired the defense secretary Wednesday in a dispute over a memo sent to Washington that enraged the army. The army has warned darkly of "grievous consequences" as a result of the standoff.

Relations between President Asif Ali Zardari and the generals have never been good but have soured dramatically in recent months.

The unsigned memo sent to Washington asked for its help in reining in the military in exchange for favorable security policies. It was allegedly masterminded by Pakistan's envoy to Washington, who has denied the accusation but resigned in a failed attempt to stem fallout from the crisis.

Pakistan's new ambassador to Washington, Sherry Rehman, met Wednesday at the State Department with Secretary of State Hillary Rodham Clinton. State Department spokeswoman Victoria Nuland called the meeting a chance to talk about "getting our relationship back on track in all of its elements in the new year."

Asked about Pakistan's political instability, Nuland said U.S. diplomats in Islamabad were monitoring the situation but insisted that these were internal matters for Pakistan to solve on its own.

"We want to see all parties in Pakistan behave in a manner consistent with Pakistan's constitution, with its democratic processes, civil discourse," Nuland said. She insisted the U.S. supports a "civilian-led government" even as it maintains "strong relations" with the Pakistani military.

"This is a matter for Pakistan to settle," she said. "I don't think it's appropriate for the United States to be in the middle of it. "

Pakistan's internal conflict adds yet another layer of complication and peril to the U.S.-Pakistani relationship, which the Obama administration insists is still key to defeating the threat posed by al-Qaida and other terrorist groups.

The relationship already is badly strained in the aftermath of American airstrikes on the Afghan border last November that killed 24 Pakistani soldiers and prompted Islamabad to close overland routes into Afghanistan for U.S. and NATO war supplies. Kirby has said that the closure has not hampered military operations in Afghanistan and that alternative routes are being used, especially to transport fuel.

Pakistan also forced the U.S. to vacate Shamsi air base in southwestern Baluchistan province. That base had been used to launch missile strikes by American drone aircraft at al-Qaida and other targets in Pakistan. After a six-week lull, a CIA drone conducted a strike against militants Tuesday.

A Pakistani official said Wednesday his government got no advance notice of the latest CIA strike. The official, speaking on condition of anonymity to discuss sensitive matters, said the attack risks adding to anti-American sentiment in his country and making it more difficult to resume close cooperation with the U.S.

American officials say that there had been no promise by Washington that drone operations would be avoided in the aftermath of anger over the November border incident but that the lull was part of a broad effort to tamp down tensions. While there has long been some level of Pakistani consent to the drone attacks, their scope and frequency has long been a source of friction between the two countries.

Pentagon officials insisted Wednesday that there is reason to hope for improvement in ties to Pakistan despite the recent series of tense episodes, including the U.S. raid that killed Osama bin Laden inside Pakistan last May.

"We know that we've hit bumps in the road over the past several months," Pentagon press secretary George Little said. "We hope to improve the relationship and get back to a place where we can cooperate vigorously on a range of matters. There are a number of issues of common concern that we share."


Associated Press writers Kimberly Dozier, Bradley Klapper and Lolita C. Baldor contributed to this report.

Robert Burns can be reached on Twitter at http://twitter.com/robertburnsAP