Islamabad, Pakistan (CNN) -- A suspected U.S. drone strike in Pakistan's tribal region killed six suspected militants on Wednesday, intelligence officials told CNN.
Two Pakistani intelligence officials said the suspected drone fired two missiles on a militant hideout in South Waziristan, one of the seven districts of Pakistan's volatile tribal region bordering Afghanistan.
The intelligence officials asked not to be named because they are not authorized to speak to the media.
Wednesday's strike is the first since March 17, when a drone strike in North Waziristan killed 44 people -- most of them civilians, two Pakistani sources said.
Such strikes have inflamed tensions between Pakistan and the United States. Pakistan has formally asked the United States for an apology for the March 17 strike.
The United States does not officially acknowledge the Central Intelligence Agency's secret drone program that targets al Qaeda militants, but it is the only country operating in the region with the capability to carry out such strikes.
A senior Pakistani intelligence official told CNN drone strikes carried out by Americans -- once widely believed to have the tacit approval and cooperation of Pakistani intelligence -- are now carried out autonomously by the CIA.
"It's unilateral action," he said.
The official expressed dismay after Wednesday's strike.
"What is this? A message (from the Americans) that it's business as usual, irrespective of what we ask of you? If it is, it's a crude way of getting your message across," he said.
The official added that Pakistan had asked the United States to curtail its drone strikes in remote tribal areas.
"We are not necessarily saying stop. What we are saying is irrespective of tactical games, this is not useful in the long run," he said. "We need a relook and to not be too trigger happy and be selective."
The drone strike came just two days after Pakistan's intelligence chief, Lt. Gen. Ahmed Shuja Pasha, met with CIA Director Leon Panetta at CIA headquarters to voice his government's complaints about CIA activities in his country.
In addition to the aerial attacks, the Pakistanis are angered by what they say is the lack of transparency about the number of CIA operatives and the extent of American intelligence activities within their country.
Although the U.S.-Pakistani relationship has been on rocky ground for some time, It came to a head when CIA contractor
Raymond Davis was arrested after killing two Pakistani men in Lahore. Although the United States said Davis was a security officer assigned to protect CIA officers, the Pakistanis maintained he was actually a spy whom they had been unaware of prior to the shooting incident.
Pakistani officials insisted this week that the United States give them details about other CIA contractors in the country.
A U.S. official who is not authorized to speak for attribution said there is a "desire to expand cooperation across a wide range of joint activities with the Pakistanis," but would not elaborate on what steps the United States is taking.
The official would not talk specifically about the drone strikes, but did say Panetta made it clear in his meeting with Pasha that "his fundamental responsibility is to protect the American people and there will not be a halt to operations that support that objective."
The official said the United States has "an obligation" to protect American troops fighting militants on the Afghanistan side of the border.
"If on the Pakistani side of the border there are bad people planning bad things against our troops, the U.S. would be remiss if it didn't take steps to thwart those activities," said the official.
The official raised the questions: "What do the Pakistani's expect? If foot soldiers are carrying bombs across the border, do they expect the U.S. to sit idly by?"
The official said if the Pakistanis don't take action against extremists operating in their territory, than the United States will.
"Pakistan needs to talk more about what they're doing and less about what they think the U.S. is doing," the official said.
Based on a count by CNN's Islamabad bureau, Wednesday's suspected drone strike was the 19th this year, compared with 111 in all of 2010.
CNN's Nick Paton Walsh contributed to this report.