Russia and Iran say U.S. 'crossed red lines' with strike on Syrian air base The statement threatened the U.S. with a response to future actions.

 -- A statement released by "the joint command operation center of Syrian allies," a group that includes Russia and Iran, warned the U.S. against further military actions in the war-torn country, following a missile strike on a Syrian air base last week.

Referring to its defense of Syrian President Bashar al-Assad's regime, the group warned that they would support Syria and its people "with all means that we have."

"The United States crossed red lines by attacking Syria, from now on we will respond to anyone, including America if it attacks Syria and crosses the red lines," the statement read. "America knows very well our ability and capabilities to respond well to them, [and] we will respond without taking into consideration any reaction and consequences."

The statement did not include critical details like what kind of military operation would cross such a red line, or what kind of response would be made on the part of Syria and its allies, but noted that they would work to "liberate" Syria from occupation.

"Rest assured that we will liberate Syria from all kinds of occupying forces, it does not matter from where they came to the occupied part of Syria," the statement warned. "Russia and Iran will not allow the United States to be the only superpower in world."

The statement warned the U.S. that allies of Syria were "closely and deeply following American forces' moves and presence" in the areas of northern Syria and northwestern Iraq, and that they will "consider them [to be] an occupying force."

Russia and Iran have backed Assad in Syria’s six-year-long conflict, as has the Shia militia Hezbollah. The United States and other Western countries have thrown their support behind rebels fighting the Syrian regime.

The statement follows heated rhetoric from American lawmakers suggesting that Syrian allies like Russia may have had prior knowledge of the chemical attack that took place in Syria last week, killing scores of civilians, including many children.

Earlier on Sunday, Rep. Adam Schiff of California, the top Democrat on the House Intelligence Committee, said on ABC News' "This Week" that Russia is "complicit" in the chemical attack in Syria.

"Absolutely they're complicit," Schiff told ABC News Chief Anchor George Stephanopoulos. "Russian intelligence may not be as good as ours, but it's good enough to know the Syrians had chemical weapons, were using chemical weapons."

The question of Russian complicity in the attack also came up in an earlier interview on "This Week" Sunday with Secretary of State Rex Tillerson.

Tillerson said he has "not seen any hard evidence" that Russians were involved in planning or carrying out the attack.

But the secretary of state said when he meets with the Russian foreign minister this week, he will bring up Russia's obligation under a 2013 agreement to ensure the Syrian government got rid of its chemical weapons.

"It agreed to be the guarantor of the elimination of the chemical weapons, and why Russia has not been able to achieve that is unclear to me," Tillerson said. "Clearly they've been incompetent and perhaps they've just simply been out-maneuvered by the Syrians."