(CNN) -

The Syrian regime says it's ready to accept support from the United States and others working under the U.N. umbrella to fight "terrorists."

The comments, by Syrian Foreign Minister Walid Moallem, were made Monday as ISIS fighters seized control of a strategically important air base in the country.

The war-racked nation has been losing control of the northeastern region to ISIS militants.

Moallem, however, warned against any unilateral action or strikes in Syrian territory without permission.

"Any effort to fight terrorism should be done in coordination with Syrian government," Moallem said.

The U.S. military and intelligence communities are gathering intelligence on the locations of ISIS leadership and its troops in Syria, two U.S. officials told CNN on Friday. The information could be used in the coming days if President Barack Obama were to authorize airstrikes against the militants in Syria.

Pentagon spokesman Rear Adm. John Kirby said on Monday, while speaking in general terms, that in order to conduct operations over Syria "you certainly want to get as much of a view on the ground as you can. You want as much situational awareness as you can."

"Satellites can provide you good visibility, but you always want closer eyes on target if you can," Kirby added.

Obama has authorized reconnaissance flights over Syria, which could begin at any point, a U.S. official told CNN on Monday.

When asked by CNN's Wolf Blitzer about how much coordination the United States would need to do with Syria to strike ISIS, Kirby said, "Not getting into the hypothetical operations, there's no intention to coordinate with Syrian authorities."

Air base seizure

The Islamic extremist group, which has taken over large areas of Syria and Iraq, wrested the Al-Tabqa air base from the Syrian military on Sunday, according to the Syrian Observatory for Human Rights, a UK-based group that monitors the conflict.

Syrian state television reported that the Syrian military had evacuated the air base in Raqqa province to regroup and was still carrying out strikes against ISIS fighters in the area.

In Iraq, ISIS claimed responsibility for three suicide car bombs that killed at least 20 people in the northern city of Kirkuk on Sunday.

ISIS said in a statement posted Monday that the bombs were a response to secular Kurdish gangs that joined the war on ISIS and their involvement in the bombing and targeting of Sunni areas.

The statement said that two of those who carried out the suicide attacks were German nationals, identified as Abu Yasser al-Almany and Abu Ibrahim al-Almany.

When contacted by CNN, the German Foreign Ministry declined comment on the ISIS statement.

ISIS, which refers to itself as the Islamic State, is part of the complex web of groups fighting in the long-running Syrian conflict -- a war that the U.N. estimates has killed more than 191,000 people.

The spread of ISIS

Rebels have been battling the regime of Syrian President Bashar al-Assad since March 2011, and the civil war has turned the country into a haven for jihadists.

ISIS has thrived amid the chaos, gaining global notoriety for its brutal tactics, including the beheading of American journalist James Foley last week.

After its break with al Qaeda this year, ISIS has grown in strength and reach. Its dramatic, murderous advance in northern and western Iraq this year provoked U.S. airstrikes aimed at helping Kurdish and Iraqi forces.

U.S. and Kurdish officials say ISIS is now under pressure in Iraq. But the extremist group continues to win significant victories in Syria.

Planes moved before base fell

Al-Tabqa air base is the last major military base in Raqqa province, which borders Turkey, to fall into ISIS' hands. The group now is now understood to have effective control over the entire province, aside from a few villages in the south.