U.S. President Barack Obama urged nations Wednesday to unite against terrorism after the deadly jihadist attacks in Brussels and said wiping out the Islamic State group was his "top priority."

Bombers killed 31 people at Brussels airport and a metro station on Tuesday. The Islamic State armed group, sometimes known as ISIL, claimed responsibility for the blasts.

U.S. President Barack Obama told Cubans in an unprecedented live television address Tuesday that he had come to the communist island to "bury" decades of Cold War conflict.

Speaking from Havana's ornate Gran Teatro on the last day of his historic visit -- the first by a U.S. leader in 88 years -- Obama compared the United States and Cuba to "two brothers that have been estranged."

President Barack Obama condemned the "outrageous" attacks Tuesday in Brussels that killed about 35 people, saying the United States would do everything in its power to hunt down those responsible.

"We must be together regardless of nationality or race or faith in fighting against the scourge of terrorism. We can and we will defeat those who threaten the safety and security of people all around the world," he said, speaking in the Cuban capital Havana.

President Barack Obama will travel to the United Kingdom and Saudi Arabia in April, a visit set to be dominated by doubts over Britain's EU membership and concerns about turmoil in the Middle East.

The White House said Obama will visit Windsor Castle -- where he will have a private lunch with Queen Elizabeth II -- and 10 Downing Street for a joint press conference with Prime Minister David Cameron.

Barack Obama will become the first U.S. president to visit Cuba in almost a century next month, a symbolic visit that will cast off one of the last vestiges of the Cold War.

The White House announced that Obama and First Lady Michele Obama will travel to the Communist-controlled island March 21-22.

U.S. President Barack Obama has urged his Russian counterpart Vladimir Putin to end air strikes against Syrian opposition forces, the White House said Sunday.

In a phone call with Putin Saturday, Obama stressed the need to quickly get humanitarian aid to besieged areas and initiating the cessation of hostilities across the war-wracked country, it said.

U.S. President Barack Obama urged Arab countries on Monday to establish inclusive governments to ensure security in a region rocked by turmoil.

"When governments truly invest in their citizens, their education, skills, and health, and universal human rights are upheld, countries are more peaceful, more prosperous and more successful," he told the opening day of the World Government Summit in Dubai.

The United States will launch a "moonshot" effort to cure cancer, President Barack Obama declared Tuesday, assigning his deputy Joe Biden to lead the effort.

Comparing the scale of the challenge to the successful U.S. mission to put an astronaut on the moon, Obama said the drive would receive the same effort as clean energy research. 

U.S. President Barack Obama on Thursday vowed not to campaign or vote for any candidate, including Democrats, who opposes tighter gun laws, as he publicly challenged critics of his policies.

In a concerted effort to garner support for contentious unilateral measures regulating the sale and purchase of guns, a sometimes combative Obama took to television to make his case.

U.S. President Barack Obama wept openly Tuesday as he urged America to wake up to the need to tackle the gun violence that claims tens of thousands of lives in the country each year.

Tears streamed down Obama's cheeks as he summoned the memory of the 20 elementary school children slaughtered three years ago in Newtown, Connecticut.