Politically isolated and unable to bridge the growing gap between leftist protesters and the rightist establishment, Bolivian President Carlos Mesa decided to offer Congress his resignation.

BY TYLER BRIDGES

LIMA, Peru - Bolivian President Carlos Mesa, in a dramatic speech Sunday night on national television, announced that he would ask the Congress today to accept or reject his resignation, saying he was fed up after the latest street protests that have shaken his politically fragile nation.

''I have decided to submit to the country -- submit for the consideration of the country, for the consideration of you, citizens of Bolivia, as I am obligated by the constitution, through the National Congress -- my resignation as the constitutional president of the republic,'' Mesa said from the presidential palace.

Alvaro García, a Bolivian political analyst, in a telephone interview from La Paz, said he wasn't sure what the Congress would do and added, ``The president decided he had no other option than to say he is willing to go home.''

Opponents and supporters of Mesa are expected to be out in force today.

Mesa's announcement was a surprise, but analysts said he felt he had no choice after the latest political turmoil: a dispute over a water contract that shut down El Alto on Friday, coca growers threatening to occupy oil fields that forced an army mobilization on Saturday to protect the fields and a threat by leftist leader Evo Morales to blockade highways and major streets throughout Bolivia to oppose the new oil and gas law favored by Mesa.

''I am not ready to prolong this shameful comedy we are in,'' the president said.

If Congress accepts the resignation, its president, Sen. Hormando Vaca Diez, would become Mesa's constitutional successor and an early election would probably be held. Mesa's term was scheduled to end in 2007.

Mesa has expressed frustration before at the social forces that have been tearing apart this nation, the poorest in South America, since violent street protests prompted President Gonzalo Sánchez de Lozada to resign in October 2003. Mesa, a political novice, had been the vice president.

Mesa has hoped that his high personal popularity ratings -- Bolivians like that he is a political independent seen as trying to do the right thing -- would allow him to hold together the weak political center.

But both the left and the right have taken increasingly extreme positions in recent weeks, leaving him like a man trying to bridge two land masses that are slowly but surely pulling apart.

The left has radicalized in El Alto, a poor satellite city on the flat rim above La Paz, over the service provided by a French-owned private water company.

LEFTISTS NOT SATISFIED

In January, Mesa canceled the contract, saying the company had not met promises to hook up enough houses with running water and sewer service.

With this move, Mesa hoped to deflate the leftist movement there. But neighborhood leaders then began demanding that Mesa expel the private company immediately, even though this might require Bolivia to pay the company $60 million in damages. Friday's strike succeeded in shutting down El Alto.

Mesa's effort to get the Congress to approve a new oil and gas law has prompted additional headaches.

Morales' Movement Toward Socialism and Sánchez de Lozada's political party, on the right, have pushed Congress to approve a measure that would effectively take natural gas holdings out of the hands of the foreign oil companies and impose a high tax on any gas any profits they earned.

In recent days, Morales threatened to mobilize supporters throughout the country to force the version he favors through Congress. Sánchez de Lozada's party leaders have said simply that they want revenge on Mesa, believing that he stabbed Sánchez de Lozada in the back to gain power.

SKEPTICAL RIGHT

Mesa has faced problems on the right in eastern Bolivia as well. The state of Santa Cruz, the business center of Bolivia, has pushed for greater autonomy from La Paz and the rest of the country.

Mesa hoped to solve that problem in January by agreeing to allow Santa Cruz to hold a public referendum later this year to decide the issue.

Reflecting the distrust toward Mesa in Santa Cruz's business community, Oscar Ortiz, general manager of the area's chamber of commerce, said Mesa's resignation announcement was a ploy.

''He's looking to strengthen himself,'' Ortiz said by telephone from Santa Cruz.