In a radio interview on Friday, the Massachusetts senator challenging incumbent George Bush in the November presidential election, also vowed to use diplomacy to build alliances in Iraq.
"I believe that within a year from now, we could significantly reduce American forces in Iraq, and that’s my plan," Kerry said. "I believe we can."
Kerry once again accused Bush of "rushing to war without a plan to win the peace".
"He pushed our allies aside. We have lost our credibility with the world," he said. "You need to have more people involved in the process.
"We have not seen this administration do the statesmanship, do the diplomacy necessary, and America's paying a very high price, both in terms of the lives of our young and the money that’s coming out of the taxpayers' pockets," he said.
Promising to do a much better job, the presidential contender said he would reduce the burden on the National Guard and reserves and their families, "who are paying a very high price for the president's rush".
Iraqi security forces could take over a large part of the country's security if they received training from other countries, he added.
Kerry also suggested that the US should play a larger role in Sudan's Darfur region, where up to 50,000 people are believed to have died in clashes since a rebellion erupted against the Khartoum government in 2003.