President Cristina Kirchner, in a move that marks a watershed in expanding the state's grip on the economy, said she will send a bill to Congress to nationalize Argentina's largest oil-and-gas company, YPF SA. Under the proposal, which declares the petroleum industry of "national public interest," Argentina's federal and provincial governments would take 51% of the company, now majority owned by Repsol YPF of Spain. The move is sure to be approved in Argentina's Congress, where the leftist Mrs. Kirchner's governing Peronist part holds a majority. The nationalization marks the culmination of a months-long battle between YPF and the Kirchner...