US President Barack Obama (R) greets French President Francois Hollande during a joint news conference in the East Room of the White House in Washington November 24, 2015. [Photo/Agencies]

WASHINGTON - President Barack Obama said on Tuesday the United States and France will stand united to fight Islamic State militants following the November 13 attacks in Paris, pledging to step up efforts to combat terrorism alongside its European partners.

"As Americans, we stand by our friends in good times and in bad, no matter what," Obama said at a news conference with French President Francois Hollande at the White House.

Hollande is trying to rally support this week for a more coordinated international campaign to destroy Islamic State. He is due to visit Moscow on Thursday.

"The United States and France stand united, in total solidarity, to deliver justice to these terrorists ... and to defend our nations," Obama said, adding that Islamic State and its ideology "pose a serious threat to all of us."

Hollande said the United States and France have agreed to step up strikes in Syria and Iraq to target Islamic State. Hollande said he and Obama agreed on the importance of closing the Turkish border to limit the movement of extremists into Europe.

Hollande's meeting with Obama follows the attacks in Paris that killed 130 people at the national sports stadium, a concert venue and bars and restaurants in heart of the French capital. Islamic State has claimed responsibility for the attack.

Obama said he and Hollande agreed that more needed to be done to combat Islamic State's efforts.

"US assistance has supported recent French strikes in Syria and we're going to keep stepping up that coordination," he said. "We will continue to do everything in our power to defend our nation."

"We will win and groups like ISIL will lose," Obama said, using an acronym for Islamic State.

"Viva la France," Obama said.

On the Syrian crisis, Obama also said that Russian strikes against moderate opposition there only serve to bolster Syrian President Bashar al-Assad's government.