Five White House hopefuls are tied atop the Republican nomination race, a national poll released Thursday showed, making it anyone's guess who will battle Democratic nominee Hillary Clinton in 2016.

The leading quintet, who include former Florida governor Jeb Bush -- who has yet to declare his candidacy -- and Senator Marco Rubio, were clustered at 10 percent support each, with none beating the early frontrunner Clinton in head-to-head matchups.

U.S. President Barack Obama offered Tunisia closer security ties Thursday, in a bid to ensure jihadists do not extinguish the brightest democratic light to emerge from the Arab Spring.

Hosting President Beji Caid Essebsi at the White House, Obama declared Tunisia a "non-NATO ally," which would allow for enhanced military cooperation and the transfer of advanced weapons. 

"Hello, Twitter! It's Barack. Really! Six years in, they're finally giving me my own account."

With that inaugural Tweet sent from a smartphone in the Oval Office before jumping on Marine One Monday, the President of the United States Barack Obama -- or @POTUS -- cast off security and bureaucratic chains in place since he was elected.

U.S. special forces killed a senior Islamic State group leader and captured his wife in a daring raid in eastern Syria, the White House announced on Saturday. 

The raid was carried out at the direction of U.S. President Barack Obama, his spokeswoman on national security matters, Bernadette Meehan said in a statement.

The U.S. Congress on Thursday sent President Barack Obama a bill to give lawmakers the power to review and potentially reject a nuclear deal with Iran.

The House overwhelmingly passed the measure, 400-25, a reflection of lawmakers' insistence on having a say in what could be a significant international accord to get Iran to curb its nuclear program in exchange for relief from economic sanctions.

The White House was briefly put on lockdown Thursday as the Secret Service detained an individual for flying a small drone in an adjacent park.

In a statement, the Secret Service said the individual was seen flying the Parrot Bebop device in Lafayette Park at an altitude of about 100 feet (35 meters).

Republican presidential candidate Marco Rubio will set out an uncompromising doctrine for wielding American power Wednesday, in the first major foreign policy address of his White House campaign.

According to remarks obtained by AFP, Rubio will vow more "clarity and consistency" in the pursuit of U.S. interests, firing barbs at Russia, China and Iran, while setting himself against years of alleged vacillation by President Barack Obama.

The White House renewed an appeal on Tuesday for information on the location of a U.S. journalist abducted in Syria 1,001 days ago.

"This week, it is with a heavy heart that we mark American journalist Austin Tice's 1,000th day in captivity," said National Security Council spokeswoman Bernadette Meehan.

French President Francois Hollande called Monday for an end to the US embargo on Cuba, during the first visit by a Western leader to the island since Washington and Havana moved to restore ties.

Addressing the half-century-old trade embargo ahead of meetings with Fidel and Raul Castro, the brothers who have ruled Cuba since its 1959 revolution, Hollande said France will do whatever possible to see that "the measures that have so badly harmed Cuba's development can finally be lifted, repealed."

U.S. President Barack Obama has no immediate plans to visit Cuba but has not ruled out making such a trip "in the year to come," the White House said Monday.

As France's President Francois Hollande touched down in Havana, Obama's spokesman Josh Earnest told reporters who asked if the U.S. leader would follow suit: "I would not rule it out."