Indian corporates eyeing US companies for mergers and acquisitions should take prior approval from the US anti-trust department to avoid legal complications, industry body Assocham cautioned today."All corporates eyeing takeover of US companies with cost exceeding $50 million should first get their deals approved by the US anti-trust department to ensure that these (deals) are not entangled in legal battles," the chamber said in a release today.Takeover of US companies in deals worth up to $50 million are exempt from pre-notification, but any transaction above this value is subject to pre-qualification from the American anti-trust department, Assocham pointed out. Even the American companies are required to take such pre-qualification, it added.Violation of the rules laid down by the department may result in heavy penalties and the transactions could also be declared as null, the association said.