A clerk works in front of a SoftBank Corp branch in TokyoBy Alina Selyukh (Reuters) – Dash Nextel Corp and Japan's SoftBank Corp stated on Wednesday they had reached a nationwide security agreement with U.S. authorities, overcoming an immense hurdle for the Eastern firm's $20.1 billion bid to keep watch over the wi-fi carrier. Even with that approval, there are nonetheless numerous regulatory, congressional and investor hurdles dealing with SoftBank prior to it will possibly shut on its plan to break into the U.S. market. One influential U.S. senator mentioned on Wednesday he used to be "carefully analyzing" the approval to see if it eased his safety concerns. …