This image from a 2013 video shows Warren Weinstein, an American development worker who was kidnapped in Pakistan by al-Qaeda and later accidentally killed in a U.S. drone strike. (AP)

The Obama administration has agreed to pay nearly $3 million to the family of an Italian aid worker who was killed in a CIA drone strike in Pakistan last year, but it has yet to reach a settlement with relatives of an American who was also killed in the attack, U.S. officials said.

The agreement with the family of 39-year-old Giovanni Lo Porto marks the culmination of nearly 18 months of negotiations since President Obama publicly apologized for the deaths of the two aid workers — who were being held hostage by al-Qaeda — and the White House pledged that their families would be compensated.

But the administration remains at an impasse with relatives of Warren Weinstein, a Rockville, Md., resident who was abducted by al-Qaeda in 2011 while working in Lahore, Pakistan, on a U.S. government development contract. Weinstein was 73 when he was killed.

Weinstein’s widow said in a statement that she was heartened to hear that the Lo Porto family had reached a settlement with the U.S. government. “We hope that this brings them some measure of closure,” Elaine Weinstein said. “As they and we know all too well, no settlement will ever replace the hurt we feel in our hearts for the unnecessary loss of our loved ones.”

The Weinstein family is continuing to work with the government to “come to closure on outstanding issues,” according to the statement.

The White House declined to confirm details of the payment to the Lo Porto family or discuss the ongoing talks with the Weinstein family. “When we announced Mr. Lo Porto’s death in a U.S. government counterterrorism operation last year, we affirmed that the United States would provide a condolence payment to his family,” said Ned Price, a spokesman for the National Security Council. “We did so knowing that no dollar figure could ever bring back their loved ones.”

Both Weinstein and Lo Porto died in a January 2015 drone attack that raised troubling questions about a CIA program that the administration has frequently touted as peerless in its accuracy and governed by rules that require “near certainty” no civilians will be killed.

The payment to Lo Porto’s family was first disclosed Friday by the Italian newspaper La Repubblica, citing documents showing that the agreement was signed July 18 and called for a payment of 1.18 million euros as a “donation in the memory of Giovanni Lo Porto.”

U.S. officials confirmed the agreement but said the actual sum was closer to 2.6 million euros, or nearly $3 million.

Weinstein’s family has been locked in a long and difficult negotiation with the U.S. government since his death was announced early last year. In recent months, the White House has played a lead role in trying to bring those talks to a close and has significantly increased the government’s initial offer of compensation.

The two sides have been divided over the process for determining the size of the condolence payment. From the outset of the talks, the U.S. government has largely declined to explain in detail how it arrived at the amount it was offering and has declined requests for an outside arbiter.

The CIA had been conducting drone surveillance of the suspected al-Qaeda compound hit in the early 2015 attack for weeks but failed to detect that Weinstein and Lo Porto were inside until after aerial footage showed two unaccounted-for bodies being removed from the rubble.

Obama pledged an investigation of the incident and was forced to issue an extraordinary public apology four months later when the two aid workers’ identities were confirmed. “I profoundly regret what happened,” Obama said in April last year. “On behalf of the United States government, I offer our deepest apologies to the families.”

The CIA faced additional criticism from senior lawmakers when it was subsequently disclosed that the agency had detected an apparent Western hostage being held by al-Qaeda months before the botched strike but did not keep that person under surveillance.

U.S. officials said that the footage showing a possible hostage was inconclusive, but lawmakers accused the agency of dropping a potential lead on an al-Qaeda captive to keep its drone resources focused on hunting suspected terrorists.

Julie Tate contributed to this report.