Argentina and Brazil are facing the possibility of short-term energy crises from a lack of natural gas needed to fuel industries and generate electricity for residents. Bolivia is sitting in the middle with the region’s largest gas reserves.

For Cristina Fernández de Kirchner, Argentina’s new president, finding solutions to the energy problems that the administration of her husband, Néstor Kirchner, helped create is among her biggest early challenges.

Bolivia, which has seen a rise in domestic energy demand, has struggled to meet its contractual obligations to supply gas to Brazil and Argentina. Brazil’s national oil company, Petrobras, which has a much larger contract with Bolivia, has been unwilling to divert any gas supplies to Argentina because of concerns here that Brazil could face its own energy shortfalls.

That changed little over the weekend, as leaders from the three countries met in Buenos Aires to discuss energy issues, with Argentina walking away with no pledges for more gas supply. The result is that both Argentina and Chile — which Argentina has cut off from gas supplies the past few years — will face severe risks of energy shortfalls this coming winter.

President Luiz Inácio Lula da Silva of Brazil promised to try to provide some electricity — but not gas — to Argentina in the coming months, as Brazil did last June and July when Argentina was struggling to supply its industries and homes.

Brazil’s foreign minister, Celso Amorim, portrayed the move last year as a “sacrifice.” He said in an interview that Brazil would not help Argentina this year if it meant “the risk of having blackouts or brownouts in Brazil.”

José Sergio Gabrielli, the chief executive of Petrobras, said that while Brazil was “sensitive” to Argentina’s energy problems, Brazil needed “every molecule” of gas it imported from Bolivia.

Those statements underscored the high political stakes for Mr. da Silva’s government. In 2000, when President Fernando Henrique Cardoso imposed energy austerity measures in Brazil, his plummeting approval ratings helped sink his party’s chances in the next presidential election. “Lula is not going to risk domestic shortages or having to ration gas to help Argentina,” said Daniel Kerner, an analyst with Eurasia Group, a global risk consulting firm based in Washington and New York.

While Argentina pays more for Bolivian gas than Brazil, Brazil’s larger contract and the importance of Petrobras have given Argentina little leverage, analysts said. In December, Mr. da Silva said that Petrobras would invest up to $1 billion in Bolivian gas over the next few years.

Mr. Kerner said Argentina had only itself to blame for its energy problems. Mr. Kirchner’s government, which took over just after Argentina’s devastating financial crisis of late 2001, maintained low energy prices at all costs to keep inflation low and the economic recovery going. That meant imposing heavy subsidies and paying more for Bolivian gas rather than charging Argentines more.

Despite Mr. Kirchner’s persistent denials last year of a growing energy problem during his wife’s campaign, the policy has begun to show cracks. Industrial production last July fell 2.7 percent from the previous year, slowing to its lowest increase since 2002. Outsiders have been reluctant to invest in Argentina’s energy sector because of high taxes and low returns caused by the government’s caps on domestic prices. As investment has faltered, energy demand has risen faster than supply.

Still, so far the gamble seems to have paid off: Mrs. Kirchner was easily elected in October as Argentina’s first female president, and the economy grew by 8 percent for a fifth straight year.

Bolivia has complicated the situation for Argentina. Bolivian gas production has been stagnant since 2006, and the country has had to adjust in order to guarantee supply of 31 million cubic meters a day to Brazil under its priority contract. It has fallen short of that lately, shipping 27 million to 29 million cubic meters a day. Exports to Argentina, meanwhile, have fallen to under three million cubic feet a day, less than half of its contract with Bolivia.

Investment in Bolivian energy has been paralyzed since President Evo Morales nationalized its natural gas industry in 2006. Bolivia’s own energy demand has grown substantially because of artificially low prices set by the government.

As Bolivian gas supplies have faltered, Mr. Kirchner, rather than risk political damage at home, chose to cut off gas supplies to Chile, creating tensions between the countries.

After taking over as president in December, Mrs. Kirchner acknowledged an energy crisis for the first time, attributing it in part to global warming. She ordered clocks moved forward by one hour, mandated the use of more energy-efficient light bulbs and required doormen in Buenos Aires to monitor residents’ air-conditioning use.

Vinod Sreeharsha contributed reporting from Buenos Aires.