By JUAN FORERO
 
BOGOTÁ, Colombia, March 7 - In what seemed a calculated political gamble, President Carlos Mesa of Bolivia offered Congress his resignation on Monday in the face of road-choking protests that he said had made the country nearly ungovernable.

"I cannot continue to govern besieged by a national blockade that strangles the country," Mr. Mesa, 51, a former journalist and historian, said in a resignation letter read on national television.

But government officials said Mr. Mesa was hoping his announcement would be rejected by lawmakers and serve as a rallying point for Bolivians tired of the relentless protests. Congress is expected to meet Tuesday morning to decide Mr. Mesa's future.

If the government is able to marshal support, political analysts say, Mr. Mesa could emerge with a mandate and avoid the same fate as his predecessor, Gonzalo Sánchez de Lozada, who was overthrown amid similar protests in October of 2003.

"The gamble is to get the people who tolerated these protests in the past to go out and say they won't tolerate it," Jaime Aparicio, Bolivia's ambassador in Washington, said in a phone interview. "It may be effective, but we'll have to wait and see."

Mr. Mesa's chief of staff, José Galindo, presented the president's resignation to lawmakers after demonstrators last week closed highways nationwide to protest a new government-supported bill they felt did not go far enough to tax the foreign oil and gas companies that are developing Bolivia's huge reserves of natural gas.

The government has proposed a new 32 percent direct tax on the production of natural gas and oil, leaving royalties at 18 percent to avoid breaking long-standing contracts with the companies. But protesters want royalties raised to 50 percent on top of the tax, as well as more control over where the gas is sold. Mr. Mesa said their proposal would drive away investors.

The president also faces an uprising in El Alto, the predominantly indigenous city where demonstrators are demanding that the authorities immediately close down a hated French-owned company that runs the waterworks, rather than phasing out its operations as the government proposed after annulling a 20-year contract in January.

Mr. Mesa's decision to offer his resignation, first made in a nationally televised broadcast on Sunday night, surprised the government's opponents.

Reached by phone in his office in the city of Cochabamba, Evo Morales, the country's most powerful indigenous leader, said he saw Mr. Mesa's announcement as a thinly veiled power play. "It is blackmail so as to not change the government's neoliberal policies," he said. Earlier, Mr. Morales had promised to step up the protests this week.

Mr. Mesa's announcement seemed to have some of the desired effect. Thousands of Bolivians gathered in front of the presidential palace on Monday morning, lamenting Mr. Mesa's decision and denouncing Mr. Morales.

In Congress, not normally a hotbed of support for the president, two powerful leaders of opposition parties, Jaime Paz and Manfred Reyes, both said Monday that Mr. Mesa should continue as president for the sake of the country.

The president of the Bolivian senate, Hormando Vaca Díez, who is next in line to become president, said he would not accept the presidency if Mr. Mesa resigned. The United States and several Latin American countries also expressed support for Mr. Mesa, worried that his resignation could plunge Bolivia into chaos.

Still, Mr. Galindo, the chief of staff, said in an interview that it was not enough for Congress to reject Mr. Mesa's resignation. He said lawmakers from all parties, including those most opposed to the government, should reach an accord that would permit the government to operate smoothly. "It cannot just be that the president goes or does not go," he said. "What we need is to come up with a national accord to permit the country to be governed."

Unless there is an agreement, Mr. Mesa will remain hobbled, analysts say.

Since 2000, when protesters forced out an American company contracted to run the water system in Cochabamba, government policy has increasingly been shaped by the size and power of demonstrations. By Mr. Mesa's own count, there have been more than 800 protests against him since he replaced Mr. Sánchez de Lozada.

Antigovernment leaders retain solid backing and have been emboldened by Mr. Mesa's repeated assurances that he will never use deadly force to control protests, as had Mr. Sánchez de Lozada.

"Mesa has to understand that governments have the right, the legitimate right, to use force," said Eduardo Gamarra, the Bolivian-born director of the Latin America and Caribbean Center at Florida International University in Miami. "You can't just burn down a building or take over a government building because you don't like government policy."