The White House said on Monday that there is little doubt that the Syrian government has used chemical weapons.

U.S. President Barack Obama is evaluating a response to the use of chemical weapons but has not yet decided on a response, said White House spokesman Jay Carney, according to Reuters.

The spokesman gave no time period for when Obama would decide.

“There is very little doubt in our mind that the Syrian regime is culpable,” said Carney, stating that it is undeniable that chemical weapons were used in a “clear violation of an international norm.”

Carney accused Syrian forces of again shelling the site of a chemical weapons attack outside Damascus soon after U.N. chemical weapons inspectors left the site, saying that “upon its return the neighborhood was again bombarded and shelled,” according to AFP.

Carney added that the events showed an “utter lack of Syrian credibility.”

The U.N. inspectors on Monday inspected the site of the alleged chemical weapons attack outside Damascus by Syrian government forces and also met the wounded in hospital.

Earlier on Monday, U.S. Secretary of State John Kerry called last week’s alleged chemical weapons attack a “moral obscenity,” asking all nations to unite against the use of chemical weapons in Syria.

“What we saw in Syria last week should shock the conscience of the world. It defies any code of morality,” Kerry said in a televised statement.

The information so far, including videos and accounts from the ground, indicates “that chemical weapons were used in Syria. Moreover, we know that the Syrian regime maintains custody of these chemical weapons,” Kerry said.

He added that United States has additional evidence of Syrian chemical weapons attacks.

Kerry said that shelling the affected area afterward was not the action of a government trying to cooperate with U.N. investigators trying to assess what happened.

“People feel that there's a sense of urgency ... but no timeline," State Department deputy spokeswoman Marie Harf told reporters in Washington, shortly after Secretary of State John Kerry’s statement.

The alleged chemical weapons attack on Aug. 21 that killed hundreds has moved the U.S. closer to military action against Syria than at any point during the bloody civil war.

Last week, Washington accused Syria of attempting to destroy evidence from the attack.

According to opposition forces, 1,300 people, including children, were killed in the attack.

Bashar al-Assad has denied that chemical weapons were used.

(With Reuters and AFP)