President Barack Obama, speaking to the grieving community of Newtown, Conn., Sunday evening said he would use every power of his office to prevent more tragedies like the Sandy Hook Elementary shootings.

NEWTOWN, Conn. — A mournful President Barack Obama said Sunday that the nation is failing to keep its children safe, pledging that change must come after an elementary-school massacre left 20 children dead.

"What choice do we have?" Obama said. "Are we really prepared to say that we're powerless in the face of such carnage, that the politics are too hard?"

Obama said that the country will "have to change."

In a vigil for the fallen, in a moment of grief that spread around the world, Obama conceded that none of his words would match the sorrow. But he declared to the community of Newtown: "You are not alone."

For Obama, ending his fourth year in office, it was another sorrowful visit to another community in disbelief. It is the job of the president to be there, to listen and console, to offer help even when the only thing within his grasp is a hug.

The massacre of 26 children and adults at Sandy Hook Elementary on Friday elicited horror around the world, soul-searching in the United States, fresh political debate about gun control and questions about the incomprehensible — what drove the suspect to act.

Privately, Obama told Connecticut Gov. Dannel Malloy that Friday was the most difficult day of his presidency.

Obama spoke on a spare stage, with just an American flag, a Connecticut state flag and a lectern bearing the presidential seal.

Police and other first responders were greeted with applause and hugs as they entered the auditorium.

Obama was addressing not only the residents of Newtown, but also a stunned nation.

A White House official said Obama was the primary author of his speech and edited his remarks on the flight to Connecticut with presidential speechwriter Cody Keenan.

Keenan helped Obama write his speech last year following the shootings in Tucson, Ariz., that left six dead and 13 wounded, including Rep. Gabby Giffords.

"As a nation, we have endured far too many of these tragedies in the last few years," Obama said in his weekly radio address Saturday. "An elementary school in Newtown. A shopping mall in Oregon. A house of worship in Wisconsin. A movie theater in Colorado. Countless street corners in places like Chicago and Philadelphia."

Just last summer, Obama went to Aurora, Colo., to visit victims and families after a shooting spree at a movie theater in the Denver suburb left 12 dead. He went to Tucson, Ariz., in January of last year after six people were killed and 13 were wounded, including then-Rep. Gabrielle Giffords, outside a grocery store.

In November 2009, Obama traveled to Fort Hood, Texas, to speak at the memorial service for 13 service members who were killed on the post by another soldier.

"We have to come together and take meaningful action to prevent more tragedies like this. Regardless of the politics," Obama said in his broadcast remarks.

After the Colorado shooting in July, the White House made clear that Obama would not propose new gun restrictions in an election year and said he favored better enforcement of existing laws.

The Connecticut shootings may have changed the political dynamic in Washington, although public opinion in favor of gun control has declined over the years. While the White House has said Obama stands by his desire to reinstate a ban on military-style assault weapons, he has not pushed Congress to act.

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