WHITE HOUSE - U.S. President Barack Obama says although the U.S.-led effort to combat Islamic State has made progress, the fight “remains difficult” and he has instructed his security team to ramp up efforts.

He said the situation in Syria and Iraq is "one of the most complex the world has seen in recent times." He noted that Islamic State "is entrenched, including in urban areas, using civilians as human shields."

He added the war in Syria is "a proxy war between regional powers, reflecting deep sectarian rivalries."

Obama made his comments after meeting with top security officials at the State Department Thursday. He said there are indications the flow of foreign fighters into Syria seems to be slowing down, making it harder for the militants to replenish their ranks.

Referring to the U.S.-Russian cease-fire set to take effect in Syria, Obama said the United States will do everything it can to help the agreement hold.

Russian Foreign Minister Sergei Lavrov on Friday hosted a meeting in Moscow of the Russian-Arab Cooperation forum, where he pledged that the gathering would focus on ending the conflict in Syria.

And in Syria, despite the looming cease-fire, the Syrian Observatory for Human Rights reports that Russian airstrikes were continuing against rebel-held areas east of Damascus Friday. The agreement does not include Syrian strikes on Islamic State or the al-Qaida-linked al-Nusra Front.

President Barack Obama, center, followed by Secret
President Barack Obama, center, followed by Secretary of State John Kerry, left, and Defense Secretary Ash Carter right, walks to a podium to speak to media after a meeting of his National Security Council (NSC) at the State Department in Washington, Feb.

More funds to fight IS

Secretary of Defense Ash Carter told the Congressional House Appropriations Committee Thursday the United States is increasing its funding for the battle against Islamic State in Syria, Iraq, Afghanistan and parts of Africa. He said his department is requesting $7.5 billion, a 50 percent increase over last year, to fight the militant organization.

Carter said the fight would encompass not just land, air and sea, but also space and cyberspace. Briefly, he confirmed reports that the military's Cyber Command unit has recently begun a new cyberwarfare campaign against Islamic State, but declined to give details in a public setting.

In recent months the intensification effort against Islamic State has included the use of additional U.S. special expeditionary forces to carry out raids, free hostages, capture IS leaders and gather intelligence.

The U.S. has said the fighting in Syria between troops loyal to President Bashar al-Assad and rebels fighting to oust him has allowed Islamic State to flourish amid the chaos and instability. But Obama seems cautious about whether the cease-fire deal will hold up. 

“If implemented, and that’s a significant if, this cessation could reduce the violence and get more food and aid to Syrians who are suffering and desperately needed.  It could save lives.”

The White House has accused Putin of fueling the civil war by helping to prop up the Assad government with airstrikes targeting opposition rebels.

The cessation agreement calls for an end to attacks and aerial bombardment and for the flow of humanitarian aid to areas under siege. 

"A lot of that is going to depend on whether the Syrian regime, Russia, and their allies live up to their commitments," Obama said. "The coming days will be critical, and the world will be watching."

FILE - Secretary of State John Kerry gestures duri
Secretary of State John Kerry gestures during a joint press conference with his Jordanian counterpart Nasser Judeh (unseen) in Amman, Jordan, Feb. 21, 2016.

Kerry: Syrian 'slaughter' continues

Earlier Thursday, lawmakers questioned Secretary of State John Kerry repeatedly about U.S. efforts to help end the fighting and humanitarian crisis in Syria during a House Foreign Affairs Committee hearing.
He said the "slaughter" of innocent people was still occurring in Syria, where bombs had been dropped on hospitals and schools.
“That has obviously occurred which is why we have pushed so hard to try to get a cessation of hostilities,” said Kerry.
The cease-fire plan is part of a broader effort, backed by the U.S. and other members of the International Syria Support Group, to help foster a political transition that could help stabilize Syria and decrease threats from Islamic State and other terrorist groups.
Stronger than al-Qaida

On the fight against IS, Director of National Intelligence James Clapper said the militant group's estimated strength now exceeds that globally of al-Qaida.
"ISIL, including its eight established and several more emerging branches, has become the preeminent global terrorist threat," Clapper told the House Intelligence Committee on Worldwide Threats.
VOA State Department correspondent Pam Dockins contributed to this report.