Suspected Times Square bomber Faisal Shahzad is shown in this undated U.S. Department of Justice photograph released to Reuters on May 19, 2010.
Pakistani authorities arrested the military officer this week, officials said. U.S. investigators have been told by Pakistani officials that the major learned of Shahzad's plans from another suspect who is accused of funding the operation, according to a senior U.S. anti-terror official.
The major has since resigned from the military, said the official, who requested anonymity because the case remains open.
"We are being told the major was aware of the plot," the senior anti-terror official said. "We don't know yet how much of a role he had, if any. He did have connections to the Pakistani Taliban."
U.S. investigators have been given only sketchy details about the major and his arrest, which was first reported Wednesday by the Los Angeles Times . A spokesman at the Pakistani embassy in Washington said Thursday that embassy officials had heard reports of this week's arrest in Pakistan, but had not been able to confirm them or obtain details.