LA PAZ, Bolivia - Lines of stranded trucks with rotting cargoes snaked through the Bolivian jungle on Monday as roadblocks set up by anti-government protesters stalled traffic and fueled fears of a food shortage in major cities.

President Carlos Mesa, who threatened to quit last week in frustration at the protests, warned the government might run out of cash to pay public salaries in just two weeks as commerce grinds to a halt nationwide due to blockades that have strengthened in recent weeks.

Indian protesters scattered boulders and tree trunks across roads, worried that Mesa's plans to open Bolivia's energy sector to more foreign investment will loot the Andean country's natural wealth with no benefit for them.

Opposition to Mesa's energy policies has turned into a rallying cry for a long list of grievances in South America's poorest country, with racial tensions, anti-U.S. sentiment and resentment over poverty all bubbling to the surface.

"This crisis is about much more than just energy. It's everybody against the government. It's not clear how much longer Mesa can last with the country paralyzed like this," said Jorge Lazarte, a political analyst.

The blockades, which have effectively cut the country in half, are preventing many goods from Bolivia's eastern agricultural heartland from reaching either the highland capital or Pacific ports for export.

"This situation is costing exporters millions of dollars a day, and most shipments of basic goods like eggs, chickens and soy aren't getting through to the rest of the country," said Carlos Dabdoub, a representative of a growing separatist movement by the eastern province of Santa Cruz.

Plans for a meeting between Mesa and opposition leaders on Monday fell apart, with the president deciding not to attend. Labor unions plan a 48-hour strike starting on Tuesday.

Mesa offered his resignation last week, then quickly withdrew it after Congress gave him a strong show of support. However, hopes that the country would stabilize have vanished.

"These blockades are paralyzing the country," Mesa said in a televised address on Sunday night. "Bolivians need to be unanimous in their opposition to these efforts to divide us."

Many opposition leaders have described the standoff as a battle by the poor Indian majority against what they see as centuries of oppression by the European-descended elite.

Mesa's predecessor, President Gonzalo Sanchez de Lozada, quit in October 2003 after a similar Indian revolt killed dozens. Opposition parties say they want Mesa to stay in office, but want more influence over his economic policy.

"The situation is exactly the same as before Mesa resigned, and you could even say it's worse," said Lazarte, the political analyst.

Mesa urged Congress to pass a new energy law that would regulate exploitation of Bolivia's vast natural gas reserves by foreign companies such as Brazil's Petrobras or Britain's BP.

However, Indian leaders are demanding a large tax increase on the companies as a condition for dismantling the blockades.