(Adds comparison to 2016 investment)

BUENOS AIRES, June 27 (Reuters) - Argentina-based Pan American Energy, a unit of BP Plc, will invest some $1.2 billion in the South American country this year, a company spokesman said on Tuesday, down from the $1.4 billion that the company had announced for 2016.

About $400 million of the 2017 investment plan is destined for oil and gas exploration in the sprawling Vaca Muerta shale formation in Argentina's southern Patagonia region, the spokesman said in a telephone interview after government news site Telam reported the company's investment plan.

Argentine President Mauricio Macri has sought to attract investment to Vaca Muerta to help close the country's costly energy deficit since taking office in late 2015.

Argentine Energy and Mining Minister Juan Jose Aranguren said in April that investment of between $6 billion and $8 billion had been confirmed in Vaca Muerta this year.

Argentine state-run oil company YPF SA said in February that it would invest $2.3 billion in the shale field this year. (Reporting by Walter Bianchi; Writing by Hugh Bronstein; Editing by G Crosse and Leslie Adler)