WASHINGTON - US airstrikes and Kurdish fighters’ fight back had broken the siege on Mount Sinjar in northern Iraq, allowing thousands of trapped members of minority Yazidi group to escape, according to Defence Department officials.A team of about 20 US troops and aid workers spent the day on the mountain and determined that an operation to rescue Iraqis who had been besieged there was probably unnecessary, the Pentagon said.“There are far fewer” refugees left at the northern Iraq location, where tens of thousands had been said to have been surrounded by Sunni Muslim extremists, and they “are in better condition than previously believed,” a Pentagon statement said, belying earlier reports about tens of thousands taking refuge under miserable conditions. Humanitarian airdrops and the nightly evacuation of Yazidis on land routes appeared to have lessened the emergency, the Pentagon said.However, Kurdish officials and Yazidi refugees said Thursday that thousands of desperate Yazidis remain trapped on the mountain. They said those still stranded on the barren, rocky slopes of Mount Sinjar are mostly the elderly, sick and very young, who were too weak to continue the grueling trek to safety in Iraq’s northern Kurdistan region and were left behind by their relatives.The Obama administration had been weighing the use of US ground forces and aircraft in an emergency rescue of the refugees, even as it sought to develop a longer-term strategy to push back militants of the Islamic State group.Administration officials have said that strategy depends on the formation of a new Iraqi government responsive to the concerns of all ethnic and religious groups, an effort that continued its rocky progress Wednesday.But the strategy also hinges on other variables, including the capabilities of Iraqi and Kurdish troops and their capacity to cooperate on the ground. European and other allies are being enlisted to provide weapons and other support, and neighbouring Sunni states will be called upon to use their influence with Iraqi Sunnis, who have been reluctant to join the fight against Islamic State militants.Once a new government is in place, “we will be providing training and equipping, security assistance and advice to Iraqi and Kurdish forces, and then we can begin to squeeze the space where ISIL is operating and start to push them back,” Deputy National Security Adviser Benjamin Rhodes said, referring to the militant group also known as the Islamic State of Iraq and the Levant.The one “limiting factor” he said, “is we don’t want to be reintroducing US forces into a combat role on the ground.” Rhodes spoke in Massachusetts at Martha’s Vineyard, where President Barack Obama is vacationing.An expansion of US military assistance to counter the Islamic State would almost certainly include the deployment of additional military advisers to Iraq, increased weapons transfers and possibly expanded airstrikes, although Pentagon officials said Wednesday that they had yet to reach a consensus on what such a mix would look like.The departure of current Prime Minister Nouri al-Maliki would not by itself trigger an influx of military aid or more US trainers, said senior Defence Department officials, speaking on condition of anonymity. Instead, the administration would be expected to wait until a new government demonstrates clear signs of support from Iraq’s many political and religious factions.In the meantime, Obama last week authorized the US military to carry out airstrikes on a highly restricted basis — only to prevent the massacre of Iraqi minorities or to neutralize threats to US personnel or property. Defence officials said they did not have clearance, for instance, to target individual Islamic State leaders.The new military deployments brought to more than 900 the number of US troops Obama had authorized to protect US personnel and facilities in Irbil and Baghdad and to assess the needs and capabilities of Iraqi forces. Of those, 864 are on the ground in Iraq.The new troops in the Kurdish region are accompanied by four V-22 Osprey tilt-rotor aircraft and an unspecified number of helicopters.