Speaking at an event in Baghdad with President Jalal Talabani and Prime Minister Nouri al-Maliki, Biden said he was thanking both U.S. and Iraqi forces "on behalf of President Obama and the American people."
"I think it's fair to say almost no one thought that was possible a few years ago," Biden said.
"Thank you for your heroic work that each one of you has done to bring about this moment," he said. "Because of you -- and it's no exaggeration to say that -- because of you and the work those of you in uniform have done -- we are now able to end this war."
During an appearance on NBC's "Today" show before the event, Biden said he's focused on helping Obama get re-elected but he hasn't ruled out his own U.S. presidential bid in 2016.
"I am never ready to close the door on anything," he said. "That's just a foolish thing to do. I learned a long time ago.
"I am intent on re-electing Barack Obama president of the United States of America," he said. "The rest will take care of itself."
Biden said the pending withdrawal of U.S. troops is a statement that "we've done our job -- ending the war we did not start, [ending] it in a responsible way [and bringing] Americans home."
After all the training U.S. forces conducted with their Iraqi counterparts, "the idea that there is a sufficient capacity to bringing down this government and all democratic processes … no longer exists," Biden said.
Any move by Iran to take control of Iraq after the U.S. pullout would be met by "world reaction," Biden said. "Not just the United States, [but] the world reacting if all of a sudden Iran was to move across its border and invade any of the countries in the region."
Talabani presented Biden and other U.S. officials with the "shield of commitment" medal during a ceremony in Baghdad honoring U.S. and Iraqi troops.
"History will record that the liberation of our country was not only an important turning point in Iraq but it was an important beginning for the region," Talabani said.
Maliki said the U.S. withdrawal will help remove the opportunity for some countries to "to interfere in the internal affairs of Iraq."
Because of the efforts of Iraq's leaders and people, "we are now able to end this war," Biden said during the ceremony at Al Faw Palace, built by Iraq's deposed despot, Saddam Hussein, who later was executed.