GrainCorp chief executive Alison Watkins resigned on Monday, just days after the Australian government blocked a takeover bid by American agribusiness giant Archer Daniels Midland (ADM) for being against the national interest. Watkins said she would leave the biggest grain handler in eastern Australia next month, with chairman Don Taylor taking on executive duties on an interim basis until a successor is found. "I have carefully weighed my options over the past two days," she said in a statement to the Australian stock market. "Given last week's unexpected developments, I feel it is in the best interests of GrainCorp, our people and customers that I move on now and allow the board to find new leadership to take the business forward into its new phase." Treasurer Joe Hockey vetoed the takeover on Friday, which would have have left 60 percent of wheat shipments from Australia controlled by three companies -- ADM, Glencore Xstrata and Cargill. It also would have put almost all the country's eastern grain export infrastructure under foreign ownership, a scenario that met strong opposition from grower groups and the National Party, which is part of Australia's governing coalition. The Foreign Investment Review Board was split on whether to green-light the takeover but Hockey decided to reject it, sparking criticism from business groups that it sent negative signals about Australia's openness to foreign investment. Taylor said Hockey's decision had come as a surprise and Watkins' departure was regrettable. "The expectation in the investment community was that ADM's offer for GrainCorp would be approved and effected in the near term," he said. "Despite the challenges of the past week, GrainCorp remains a great company, with exciting opportunities ahead."