CAMP VICTORY, Iraq — Vice President Joe Biden today thanked U.S. and Iraqi troops for sacrifices that he said allowed for the end of the nearly nine-year-long war, even as attacks around the country killed 20 people, underscoring the security challenges Iraq still faces.

Biden’s comments came during a special ceremony at Camp Victory, one of the last American bases in this country where the U.S. military footprint is swiftly shrinking. The ceremony was hosted by the Iraqi government as a way to commemorate the sacrifices of U.S., Iraqi and coalition forces during the nearly nine-year-long war.

“Because of you and the work that those of you in uniform have done, we are now able to end this war,” Biden told the hundreds of American and Iraqi service members assembled at Al Faw palace that was built by Saddam Hussein.

Joined by Iraqi Prime Minister Nouri al-Maliki and President Jalal Talabani, Biden said the United States takes “immense” pride in what American troops have done in Iraq. He said they are leaving with their heads held high.

Biden’s visit to Iraq, which started on Tuesday, is meant to chart a path for a new U.S. relationship with a country that is home to billions of barrels of oil reserves and more closely aligned with neighboring Iran than the U.S. would like.

But even as the remaining American troops prepare to leave by the end of the year, violence and instability are still a constant in Iraq, albeit dramatically less so than at the height of the conflict.

Two attacks today in Iraq’s northeast killed 20 people and wounded 32.

Iraqi security officials maintain that they are fully prepared for the American withdrawal, which is required under a 2008 security pact between the U.S. and Iraq. About 13,000 U.S. troops are still in the country, down from a one-time high of about 170,000. All troops will be out by the end of the month.