9/11 20th anniversary: National unity, U.S’ greatest strength, says Biden (See iconic pictures)

“In the days that followed Sept. 11, 2001, we saw heroism everywhere, in places expected and unexpected.

“We also saw something all too rare: a true sense of national unity,” Biden said in the video message posted on Twitter on Friday evening.

“In the battle for the soul of America, unity is our greatest strength. Unity doesn’t mean we have to believe the same thing, but we must have a fundamental respect and faith in each other and in this nation,” the president said.

“The 9/11 generation is stepping up to serve and protect in the face of terror … to show everyone seeking to do harm to America that we will hunt you down and we will make you pay.

“That will never stop,” Biden said.

The president said that “the darker forces of human nature” also emerged following the attacks, namely “fear and anger.”

“Resentment and violence against Muslim Americans, true and faithful followers of a peaceful religion,” he said.

But the country cannot allow itself to be divided. “Unity is what makes us who we are – America at its best.”

White House spokesperson Jen Psaki said that on Saturday, the president and the first lady would “honor and memorialise the lives lost with travel to all three sites of the 9/11 attacks, visiting New York City; Shanksville, Pennsylvania; and the Pentagon.”

The president was set to visit ground zero in New York City, the Pentagon and the memorial outside Shanksville, where one of the four hijacked planes crashed after passengers attempted to regain control of the aircraft, the White House said.

The al-Qaeda plane hijackings were the single worst attack on U.S soil in the country’s history.