Indonesia yesterday said it would seize Asia's largest undeveloped gas block from ExxonMobil and ask Pertamina, the state-owned energy group, to prepare a feasibility study to take over the field. The latest move in a three-year dispute between Jakarta and the US energy group was made after talks with Exxon about the Natuna D-Alpha field became deadlocked over tax issues, the extension of a contract and how to split the gas, said Purnomo Yus-giantoro, Indonesia's energy minister.