Top U.S. officials have reached out to a leading Vietnam war scholar to discuss the similarities of that conflict 40 years ago with American involvement in Afghanistan, where the U.S. is seeking ways to isolate an elusive guerrilla force and win over a skeptical local population.

The overture to Pulitzer Prize-winning historian Stanley Karnow, who opposes the Afghan war, comes as the U.S. is evaluating its strategy there.

Among the concerns voiced by historians is the credibility of President Hamid Karzai's government, which is widely perceived as being plagued by graft and corruption. They draw a parallel between Afghanistan's presidential election on Aug. 20 and the failed effort in Vietnam to legitimize a military regime lacking broad popular support through an imposed presidential election in 1967.