Operation Lightning Resolve is "kicking off as we speak," Barno told the Associated Press from his headquarters in the Afghan capital, Kabul. Barsno said the operation contains enough "offensive punch" to keep militants off-balance and includes targeted, intelligence-driven raids.
A 2,000-strong Marine force, which has attacked Taliban militants in their southern stronghold since March, is in the process of leaving the country, Barno said.
The remaining 17,000 soldiers will try to fill the vacuum and intensify cooperation with the United Nations. The international body is helping organize the Oct. 9 presidential poll and has assisted in registering more than 7 million voters.
"Now we'll be shifting our efforts to helping to build the required security going into the election itself," Barno said. "We should expect that we have to fight to get to these elections."
U.S. forces are expected to provide security across the southern and eastern regions where the Taliban fighters have been most active, leaving Afghan police and soldiers to protect polling stations.
Despite heavy losses in clashes with Marines and the use of humanitarian aid to persuade villagers to provide intelligence, rebels continue to operate widely along the country's southern border.
In addition to American and Afghan efforts, NATO is expected to bulk up its 6,500-strong peacekeeping force now centered in Kabul and fan out across the country to the relatively peaceful north in the run-up to the vote.
The election is seen as a key step on the war-shattered country's path to recovery. In addition, officials hope the election will be a major success following the American-led assault on the country that toppled the hard-line government, but failed to capture al-Qaida head Osama bin Laden or Taliban leader Mullah Mohammed Omar.
Efforts to track down bin Laden and his top aide, Ayman al-Zawahiri, continue to be a top priority, Barno said, but the American general added there was "zero credibility" to speculation that the military was under political pressure to deliver bin Laden before U.S. elections in November.
With the Afghan government unable to reassert control in remote border areas, U.S. troop strength would remain at about 17,000 for an extended period, said Barno.
"A counterinsurgency strategy does not achieve success in three months or six months," he said. "These are longer term, sustained strategies."