Secretary of State John Kerry said Thursday that US drone strikes in Pakistan could end "very soon", in unusually outspoken remarks welcomed in Islamabad but immediately downplayed by American aides.
It is the first time such a senior member of the US administration has indicated there could be a definitive end to the programme, which the CIA has in the past called an effective counter-terrorism weapon.
But the strikes are a major thorn in often fractious ties between Islamabad and Washington, and are officially condemned by Pakistan as a violation of sovereignty and international law.
Kerry waded into the row at the tail end of a visit to Islamabad, in which he announced that Washington was reviving strategic dialogue with Pakistan for the first time after a series of crises in 2011.
Asked in an interview by state-run PTV whether the strikes could end, Kerry said: "I think the program will end as we have eliminated most of the threat and continue to eliminate it."
Pressed on whether a timeline was envisaged, Kerry replied: "Well, I do. And I think the (US) president has a very real timeline and we hope it's going to be very, very soon."
Pakistan's top diplomat Sartaj Aziz on Thursday demanded a halt to drone strikes that have already decreased.
But US officials immediately sought to downplay Kerry's remarks.
State Department spokeswoman Jen Psaki said that the number of drone strikes had declined owing to the drawdown of American troops from Afghanistan and because of progress in curtailing the Al-Qaeda threat.
"Today the secretary referenced the changes that we expect to take place in that programme over the course of time, but there is no exact timeline to provide," she said in a statement.
Pakistan's new government led by Nawaz Sharif is likely to seize upon Kerry's remarks as a coup.
A spokesman for the foreign ministry late Thursday welcomed Kerry's remarks, saying it was Islamabad's long-standing position that they should stop.
Kerry's television remarks strayed from what he told a press conference with Aziz, when he tackled complaints about drones by pointing the finger at Al-Qaeda leader Ayman al-Zawahiri, believed to be based in Pakistan.
"An Al-Qaeda leader like Al-Zawahiri is violating the sovereignty of this country. And when they attack people in mosques and blow up people in villages and market places they are violating the sovereignty of the country," he said.
On Afghanistan, he said he was confident that Washington and Kabul would reach a long-term security agreement that would allow American troops to remain in the country beyond 2014.
"We're making progress, we're working on it. I am personally confident that we will have an agreement," Kerry said.
Afghan President Hamid Karzai suspended talks on the deal in June, furious that a Taliban liaison office in Qatar appeared to have been opened as an embassy for a government in waiting.
"Let me be clear: the US is drawing down not withdrawing," Kerry said.
There are concerns that a complete departure of foreign troops in late 2014 could leave Afghan government troops too weak to contain a Taliban insurgency and possibly see the country slide back into civil war.
Kerry's visit announced the resumption of so-called strategic dialogue between Pakistan and the United States, and he invited the newly elected Sharif to hold talks with US President Barack Obama in the autumn.
It will be the highest level talks between the two sides since January 2011, after which US troops found and killed Al-Qaeda leader Osama bin Laden in Pakistan in May 2011.
In November 2011, US air strikes mistakenly killed 24 Pakistani soldiers along the Afghan border, leading Islamabad to shut down NATO ground supply lines for seven months.
Kerry said it was time to put the relationship on a stronger footing.
Sharif has made economic growth and resolving the energy crisis the top priority of his new administration, but Kerry also stressed that prosperity depends on doing more to eliminate militant havens.
"Pakistan cannot realise its full economic potential until it overcomes extremists," Kerry told the news conference.
"The choice for Pakistanis is clear: will the forces of violent extremism be allowed to grow more dominant, eventually overpowering the moderate majority?"
Kerry paid tribute to Sharif's election, which marked the first time that an elected civilian Pakistani government had completed a full term in office and handed over to another at the ballot box.
Sharif described Kerry as a "wonderful friend".
Kerry also met the outgoing President Asif Ali Zardari and army chief General Ashfaq Kayani.