Petrobras, Brazil's state-run oil company, plans to invest more than $5bn in Bolivia's gas sector in joint ventures with YPFB, the state energy company, bringing much-needed capital to a sector that has seen a dramatic fall in foreign investment in recent years.The announcement is a boon for President Evo Morales, who took office last month on a pledge to nationalise the gas industry by securing the involvement of the state as an equal partner with international energy companies."We are working on a programme of investments in association with YPFB, with the government, of more than $5bn [€4.2bn, £2.9bn) over the next five or six years," said Néstor Cerveró, a director of the Brazilian company, after meetings with YPFB and government officials in La Paz.Mr Cerveró said Petrobras would sign an initial deal with YPFB by the end of the month that would include partnership agreements on gas production, industrialising the sector, thermoelectric power and biofuels.Andrés Soliz Rada, Bolivia's hydrocarbons minister, said the agreement would contain specific pledges on a project to build a gas-chemical centre on the Bolivia-Brazil border, the participation of YPFB in two refineries operated by Petrobras, the sale of natural gas and a new contract to operate in Bolivia. Mr Soliz said the government would speed up the process of defining rules to govern the sector. "We will accelerate the structural reforms we need to start a dialogue," he said, adding that these would demonstrate that "the state is the absolute owner of hydrocarbons".That may alarm other energy companies operating in Bolivia, such as Repsol (NYSE: REP - News) , Total, British Gas and BP. All foreign investors in the gas sector apart from Petrobras have signalled that they could go to international arbitration over a hydrocarbons law passed last year that imposed higher taxes on existing contracts. The government's relations with most international investors have deteriorated markedly since the to power.Also last week, Jorge Alvarado, YPFB chairman, said he would shortly make public evidence that Repsol, one of the biggest foreign investors, had smuggled more than $6bn-worth of petrol out of Bolivia during 2004 and 2005 to avoid tax charges. The Spanish company denied the allegation. Moreover, Mr Morales said that if his plans were resisted, he would call on the country's powerful street protest movements to mobilise in support of nationalisation. Blockades demanding the nationalisation of gas forced out former President Carlos Mesa last June.Brazil is Bolivia's biggest gas customer. Petrobras transports two-thirds of Bolivia's daily gas production to its eastern neighbour, supplying some 40 per cent of Brazil's domestic consumption.In addition to the Brazilian state company's two refineries, which account for 95 per cent of the Bolivia's refining capacity, Petrobras also owns a quarter of its petrol stations and a significant pipeline network.