Cozy warm Middle-East winter sunshine seemed not able to soothe the coldness and gloom shedding on U.S. military's Camp Victory Thursday in conflict-battered Iraqi capital city of Baghdad.

The visiting U.S. Vice President Joe Biden, at the ceremony held in Baghdad to honor U.S. and Iraqi troops for their sacrifice, reiterated the pledge to fully withdraw the remaining around 13, 000 U.S. soldiers before the end of the year.

"At the end of this month, we will keep our promise to remove our remaining troops from Iraq," Biden told hundreds of U.S. and Iraqi servicemen gathering at the huge Faw palace, built by Saddam Hussein within the sprawling base area.

Biden's remarks, coming out one month ahead of the Dec. 31 withdrawal deadline, turned out to be the final clinch on the disputed exit plan.

Baghdad and Washington inked a security pact called Status of Forces Agreement in late 2008, which slated the complete pullout of U.S. troops for Dec. 31.

U.S. troops exit from all Iraqi cities in 2009 and ceased combat missions in 2010.

However, the U.S. authorities, for much of the year of 2011, had been pushing for 5,000 to 15,000 troops to stay in Iraq after the deadline.

Washington expressed concern over the security situation in the wake of the troop pullout.

But many analysts believe the reluctance is due to that the United States is hardly willing to abandon this country with much affluent oil reserves, which also neighbors both Iran and Syria.

Baghdad and Washington failed earlier this year to come to an agreement on keeping the small American military presence in Iraq next year.

At one stage, the two sides seemed to be nearing a compromise which allows a small amount of U.S. forces to act as trainers and observers in the conflict-laden northern Kurdish autonomous region.

But the agreement failed as Washington insisted on the legal immunity for the remaining servicemen in Iraq, which, to the Iraqi government, would be a damage to its sovereignty.

On Oct. 21, U.S. President Barack Obama announced that all U.S. troops stationed in Iraq will pull out of the country by the end of this year, and the Iraq War will be over.

Some 13,000 U.S. troops remain, down from a one-time high of about 170,000.

These remaining troops are seen moving out almost on a daily basis, and the U.S. military bases are handed over to Iraqi security forces one after another.

However, the United States will still have a massive presence in Iraq, including its largest embassy in the world and offices in the northern cities of Irbil and Kirkuk and the southern oil port city of Basra.

Negotiations on assigning U.S. military trainers will be resumed after the withdrawal deadline, an Iraqi government source told Xinhua on condition of anonymity, adding that it was agreed during Biden's blitz tour in Baghdad.

Security worries are mounting as nearly 20 people were killed in separate terror attacks all over Iraq on Thursday while Biden was expressing the gratitude to the sacrifice the U.S. and Iraqi servicemen have been making since the start of the war in 2003.

According to official statistics, 100,000 to 110,000 people were killed in Iraq during the war, including 4,483 U.S. troops.

Biden said on Thursday at Camp Victory that the U.S.-Iraq relationship which has long been "defined by the imperative security alone, is now giving the way to new and more normal relationship between two sovereign nations seeking to build a future together."

Iraqi Prime Minister Nuri al-Maliki said, "the U.S. troops' withdrawal from Iraq as scheduled is a historic victory to our negotiation option that we adopted in dealing with the issue of foreign troops' presence in Iraq."