tally@ (Adds comment from Mesa, context)
LA PAZ, Oct 26 (Reuters) - Bolivian President Evo Morales on Saturday vowed to hold a run-off election if an audit of a vote count that gave him an outright win turns up evidence of fraud, as he sought to calm a sixth day of protests and international criticism over his disputed re-election to a fourth term.
Morales, already Latin America's longest-serving president, is the lone survivor of a group of fiery leftist leaders who took office in the previous decade, most of whom have since been replaced by right-leaning governments.
He has overseen a rare period of economic and political stability in South America's poorest country. But charges of vote-rigging lodged by the opposition and doubts about the legitimacy of the vote raised by official observers threaten to dog his 2020-2025 term and tarnish his reputation as a democrat.
In a speech at a military event, Morales invited countries in the region that have called for him to hold a run-off vote - the United States, Brazil, Argentina, Colombia - to take part in an audit of the official tally.
"Let's do an audit vote by vote," Morales said in the coca-growing region of Cochabamba. "I'll join (the audit). If there's fraud, the next day we'll convene a second-round" election, he added in comments broadcast on state TV.
Shortly after Morales spoke, his chief rival in the race Carlos Mesa, a former president, announced his supporters were forming a commission to pressure the international community to not recognize the election's results.
Brazil, landlocked Bolivia's biggest trade partner, has already said it would reject Morales's win until the regional group Organization of American States (OAS) finishes an audit of the vote count that has not yet started.
The European Union and Washington-based OAS, both of whom sent observer missions to Bolivia, have also pushed Morales to convene a second-round vote to calm unrest and restore credibility to the election.
Protesters blocked roads in parts of the highland capital of La Paz on Saturday, chanting "fraud" and waving Bolivia's red-yellow-and-red flag as anti-government strikes continued in different cities in the South American country.
The country's embattled electoral board, the Supreme Electoral Tribunal (TSE) and Morales' government have both denied any foul play and invited the OAS to audit the official tally. But they have not said whether they would accept the OAS' condition for the audit's conclusions to be legally-binding.
Peru said on Saturday that it would take part in the audit at Bolivia's request, but it called for the process to be carried out respecting Bolivian laws.
The vote count by the TSE at 100% on Friday showed Morales had 47.08% of votes versus Mesa's 36.51% in a crowded race of nine candidates. That gave him the 10-point lead needed to face Mesa in a Dec. 15 second-round vote, when the opposition would likely rally behind Mesa to defeat Morales.
The TSE sparked an uproar after the election on Sunday when it halted publication of a quick vote count that showed Morales headed to a second-round with Mesa. When the quick count resumed after an outcry, it confirmed Morales' prediction on Sunday that he would pull off an outright win with the help of rural votes.
Mesa's campaign has also said that it has found 100,000 votes that should have been annulled due to irregularities but instead swung in Morales' favor.
"This is a scandalous fraud never seen before. That's why the people are reacting," retiree Fredy Salinas, 67, said as he bought vegetables in a market in La Paz. "The people in the government are really shameless."
Morales said his detractors were "envious" of his achievements and accused the opposition, without providing evidence, of trying to stir up unrest to try to unseat him illegally. "With lies and tricks they're trying to instigate hatred and racism," he said. (Reporting By Vivian Sequera and Daniel Ramos Editing by Chizu Nomiyama and Marguerita Choy)