US envoy Cameron Munter had a heated argument with the CIA station chief in March 2011 over a proposed drone strike against militants on the Pakistani side of the Afghan border, The Associated Press reported on Tuesday.

The envoy wanted him to call off the strike, fearing that its timing coming only a day after Islamabad freed CIA contractor Raymond Davis would further damage ties with Pakistan. But the CIA station chief and his bosses turned down the request.

The Associated Press noted that the March 17 attack helped send the US-Pakistan relationship into a tailspin from which it has not recovered.

“When the doors are closed they are shouting at each other, but once the doors are open they are congenial in front of the embassy staff,” said one official.

The hard-charging station chief also clashed with the head of the Inter Services Intelligence, over drone strikes, said a Pakistani official.

A US official familiar with the issue played down the tension. “It is very, very rare for the chief of mission to express concern about any particular operation,” the official said, referring to the ambassador. “When concerns are raised, they’re always given close consideration.”

Munter must sign off on every planned drone attack in Pakistan, although he rarely voices an objection, said a former aide to the ambassador. If Munter disagrees with a planned strike, the CIA director can appeal to him, said two US officials.

Clinton can also weigh in, and has done so at least once, one US official said. On March 17, Munter used the embassy’s secure line in an attempt to stop an imminent drone strike. His concern was that the strike would set back Washington’s already shaky relations with Islamabad, said the former aide and a senior US official. The Davis case had left bad feelings on both sides. On January 27 in Lahore, Davis shot to death two Pakistanis who he said were trying to rob him, enraging many people in a country where anti-American sentiment is high. The US insisted Davis had immunity from prosecution, but he was not released until March 16 under a deal that compensated the victims’ families. Pakistan’s security agencies came under intense domestic criticism for freeing him.

Munter’s request went to the State Department and was forwarded to then-CIA director Panetta, now secretary of defence, who insisted on going ahead, said the officials. It is unclear whether Clinton was involved in the decision. The former aide said the strike reflected the CIA’s anger at the ISI, which it blamed for keeping Davis in prison for seven weeks. “It was in retaliation for Davis,” the aide said.