By Mitra Taj
LIMA (Reuters) - Pedro Pablo Kuczynski was on track to become Peru's next president on Thursday after a near-final vote tally gave him a narrow lead in the country's tightest election in decades, although his rival Keiko Fujimori had yet to accept defeat.
Outgoing President Ollanta Humala and the leaders of Colombia, Chile and Argentina congratulated Kuczynski, a former investment banker, after the results were announced.
The centrist economist said he would wait for a complete count before claiming victory as thousands of disputed or unclear ballots remain uncounted.
A mere 41,964 votes separated the two business-friendly candidates, underscoring the divided legacy of Fujimori's father, imprisoned former authoritarian leader Alberto Fujimori.
While the gap has fluctuated somewhat in recent days, Fujimori has trailed throughout the vote count.
"We take this virtual verdict with much modesty because Peru has many challenges ahead," Kuczynski, 77, said in a news conference as supporters cheered him.
Kuczynski won 50.12 percent of all tallied votes while Fujimori had 49.88 percent, the electoral office ONPE said. However, 0.2 percent of ballots had been questioned and could not be counted.
Members of Fujimori's conservative party said earlier that electoral authorities should annul bundles of ballots, some of which had already been included in official tallies, because they had detected irregularities at several polling stations. The lawmakers said they would accept the official results, however.
The head of ONPE said disputed ballots would be settled by special electoral panels "soon."
Some 152 bundles of ballots remained under review by authorities late on Thursday. However, with each bundle holding up to 300 votes, they would only be enough to offset Kuczynski's lead if nearly all were decided in Fujimori's favor.
It would be Fujimori's second consecutive narrow loss in a presidential runoff race, after outgoing Humala defeated her in 2011. Humala could not run again because of term limits.
On the campaign trail, Fujimori tried to distance herself from the controversial policies and actions of her father, who is now serving a 25-year sentence for graft and human rights abuses during his 1990-2000 rule. But she never acknowledged he committed any crimes.
Both Kuczynski and Fujimori promised to continue the free-market policies that the elder Fujimori introduced in the early 1990s and that three successive democratic governments kept intact in the global minerals exporter.
A former prime minister and the son of European immigrants, Kuczynski is more liberal on social issues than Fujimori. He promises to secure investment for infrastructure projects that would restore growth to Peru's economy.
(Additional reporting By Caroline Stauffer, Teresa Cespedes and Ursula Scollo; Editing by Tom Brown and Kieran Murray)