Major world powers in the Group of Seven (G7) nations are preparing to call on oil producing nations such as OPEC to hike crude output to ease pressure on prices on world markets, Finance Minister Pierre Moscovici said late Tuesday.  Speaking on "TF1" channel, the minister said that he had agreed with other G7 nations to urge producers to help bring prices down by increasing output.  "I have just reached agreement... to sign a statement calling for an increase in production by oil producing countries in order to reduce petrol prices," he said.  France announced on Tuesday that it was implementing price cuts for petrol at the pump, a move that is to be joined by oil company Total and fuel suppliers.  Petrol and diesel costs will drop by between four Eurocents and six Eurocents in a programme that will cost the government around Euros 300 million (USD 375 million), with suppliers assuming the remaining costs. The price reduction is to last for three months.  Oil prices are again expected to spike this week as supplies from the Gulf of Mexico are being disrupted by Tropical Storm Isaac and hurricane conditions regularly hamper output in the summer in the US.  The call by the G7 is officially to be circulated this week. The G7 is made up of the United States, Canada, Britain, France, Japan, Germany and Italy.