Barack Obama has said he will take a tough, direct diplomacy toward Iran and Russia as he accepted the Democratic Presidential nomination.

Obama, who was speaking before nearly 84-thousand supporters in Denver Thursday, vowed to end what he called "Russian aggression".

"I will rebuild our military to meet future conflicts. But I will also renew the tough, direct diplomacy that can prevent Iran from obtaining nuclear weapons and curb Russian aggression," the Illinois senator added.

The presidential nominee told delegates he would reverse George Bush's failed policies - and be ready to face military conflicts.

Russian Prime Minister Vladimir Putin had earlier accused the US of having opened the South Ossetia conflict to help invigorate the US presidential race with a specific view to boost the chances of Sen. John McCain for the White House.

Obama stood on the cusp of becoming the first African-American presidential nominee for a major US party after his ex-rival Hillary Clinton freed her delegates to vote for him on Wednesday.

RB/MMN