WASHINGTON - The US negotiator attempting to persuade Afghan President Karzai to sign a long-term Bilateral Security Agreement according to Washington’s timetable believes his efforts are doomed to failure, according to a report in a leading American newspaper.In a classified cable transmitted in recent days, Ambassador James Cunningham wrote that he did not think Karzai would agree to sign the agreement before Afghanistan’s presidential election in April. The Washington Post which has seen the correspondence said that relations between the two countries are already near breaking point over the refusal to sign the security deal to shape the US military presence after most troops leave this year. The United States wants the Afghanistan government to sign the agreement in matter of weeks if a contingent of US troops is to remain there after 2014, the White House said on Monday.Without a deal, the United States could pull out all troops, the “zero option,” leaving Afghan forces to battle the Taliban on their own. Karzai has called that an empty threat and suggested any security deal could wait until after the April elections. The United States has 46,000 troops in Afghanistan, but that figure is set to fall to 34,000 by early 2014.In the diplomatic cable, Cunningham reportedly says he did not think Karzai would agree to sign the pact before a presidential election scheduled for April. A senior State Department official said, “We cannot comment on alleged classified documents.” But the official said, “We continue to urge President Karzai to sign the BSA promptly.”Last year, Karzai stunned US officials by making a new series of demands and suggesting that the agreement could be signed after his successor was elected. The demands include US release of Afghans detained at Guantanamo Bay, Cuba and Washington persuading the Taliban leadership to engage in peace talks with the Karzai government. Meanwhile, a US official said that seventy-two prisoners to be freed by the Afghan government are “dangerous criminals” with evidence linking them to terror-related crimes.State Department spokeswoman Jen Psaki, responding strongly to the decision of the government of Afghan President Hamid Karzai to release the 72 detainees from Bagram prison, expressed US concerns over the decision to release them without their cases being referred to the Afghan criminal justice system.“As you may also know, these 72 detainees are dangerous criminals against whom there is strong evidence linking them to terror-related crimes, including the use of improvised explosive devices, the largest killer of Afghan civilians,” she said in her media briefing Thursday.Psaki said the insurgents’ impending release also “undermines Afghanistan’s court system and rule of law.” A statement from Karzai on the prisoner release decision following a review meeting said no evidence was available to prove they had any ties to insurgent activities.The latest development puts further strain on US-Afghan relations, which are already under pressure because of Karzai’s refusal to sign the bilateral security agreement needed by the United States and NATO to decide how many of their troops are to remain in Afghanistan after the coalition forces end their combat operations at the end of this year.Reuters adds: US forces in Afghanistan have accidentally shot dead a four year old boy, Afghan officials said on Friday, the latest violence to strain ties between the uneasy allies.The Afghan-US relationship has been damaged by President Hamid Karzai’s refusal to sign a bilateral security deal that would pave the way for a US military presence after the withdrawal of most foreign troops this year.The United States has said its troops cannot remain without a deal. Their complete departure of US troops would leave Afghan security forces on their own to battle the Taliban.Karzai is demanding that the United States end all unilateral military operations on Afghan territory - among other things - before the pact is signed, because they cause avoidable civilian deaths.“We have called ... for an absolute end to ISAF/NATO military operations on homes and villages in order to avoid such killings where innocent children or civilians are the victims,” the president’s spokesman, Aimal Faizi, said when commenting on the death of the boy.The International Security Assistance force (ISAF) is Afghanistan’s NATO-led force. It is dominated by US troops.A spokesman for the governor of the southern province of Helmand told Reuters that US Marines based in the violence-plagued province mistakenly shot the boy on Wednesday because visibility was poor.“As the weather was dusty, the Marine forces based there thought he was an enemy and opened fire. As result of mistaken fire, he was killed,” the spokesman, Omar Zwak, said by telephone.A spokesman for the NATO-led force said the matter would be investigated and all possible measures were taken to avoid civilian casualties.Separately, two US service members and a civilian were killed in an aircraft crash in eastern Afghanistan on Friday, the NATO-led force said.“At this time, there are no indications of enemy involvement in the cause of the aircraft mishap,” the force said.