US President Barack Obama said Washington is hitting the Takfiri group, ISIL (so-called Islamic State in Iraq and Levant) ‘harder than ever’.

US President Barack Obama said Washington is hitting the Takfiri group, ISIL (so-called Islamic State in Iraq and Levant) ‘harder than ever’.

Sounding a notably more strident tone, Obama said that the United States and its allies were taking the fight to ISIL extremists in Iraq and Syria, but admitted that progress needed to come faster.

"We are hitting ISIL harder than ever," said Obama, in a second address following the seemingly Islamic State-influenced attack in San Bernardino, California that has raised questions about his strategy.

"As we squeeze its heart, we'll make it harder for ISIL to pump its terror and propaganda to the rest of the world," Obama insisted at the Pentagon, after meeting top military and national security advisors.

Listing eight ISIL figures killed in coalition operations, Obama issued a stern warning: "ISIL leaders cannot hide and our next message to them is simple: You are next."

Obama said that US special forces were now in Syria and were helping local groups squeeze the ISIL group's proclaimed "capital" at Raqa.

Meanwhile, he said, Iraqi forces were moving to take Ramadi, "encircle Fallujah and cut off ISIL's supply routes into Mosul."

From the air, Obama said the United States and its allies had begun targeting "oil infrastructure, destroying hundreds of their tanker trucks, wells and refineries."

"Since the summer, ISIL has not had a single successful major offensive operation on the ground in either Syria or Iraq," Obama said.

Even before the December 2 attack by an extremist husband and wife in California killed 14 people, polls showed that more than 60 percent of Americans disapproved of the way Obama is handling the Islamic State and the broader terror threat.

According to a Wall Street Journal/NBC poll published Monday, Americans now view national security as a top priority.

The same poll found that Obama's own job approval ratings were at the lowest level this year, at 43 percent.

That is a major shift since Obama's first term in the White House, when he was hailed for authorizing a high-risk special forces raid that killed Osama bin Laden.