WASHINGTON: President Joe Biden, with a grief in his voice, pledged on Thursday the United States will accountable those responsible for two attacks at the Kabul airport in Afghanistan and said he had asked the Pentagon to develop plans to strike back at them. In the blast 13 American troops and scores of civilians were killed, Biden mentioned that it was the worst day of casualties for US forces there in a decade. ISIS-K, an associate of militants who previously battled US forces in Syria and Iraq, claimed responsibility for the attack. “We will not forgive, we will not forget. We will hunt you down and make you pay, We will not be deterred by terrorists, we will not let them stop our mission. We will continue the evacuations,” Joe Biden said in remarks at the White House.. Biden said “We will find ways of our choosing, without large military operations, to get them.”He ordered flags at the White House and public buildings around the country to be lowered to half staff. He appeared to be fighting back tears and his voice fissured with emotion as he talked about the American “heroes” who died. “It’s been a tough day,” he said. Biden said he had told the US military: “Whatever they need, if they need additional force, I will grant it.” Biden defended the handling of his most serious foreign policy crisis, saying ultimately it is his responsibility while assigning some blame to his forerunner, Republican Donald Trump, for the 2020 agreement Trump concluded with the Taliban.