WASHINGTON - US President Barack Obama said on Wednesday that he has not made a decision about how to respond to the alleged use of chemical weapons in Syria's internal conflict.

"I have not made a decision," the president said in an interview with the "PBS News Hour" at the White House, reiterating he is weighing options in the wake of the claimed chemical attack in the suburbs of Damascus, capital of Syria, on August 21, in which, as many as 1,300 people were reportedly killed.

But he said the international norm against the use of banned weapons needs to be "kept in place."

"We have concluded that the Syrian government in fact carried these out, and if that's so, then there need to be international consequences," he added. "I have no interest in any kind of open-ended conflict in Syria."

The UN chemical weapons inspectors on Wednesday continued checking sites of the alleged attacks while CIA and the Pentagon working to gather more human intelligence tying Syrian President Bashar al-Assad to the attack.

Secretary General Ban Ki-moon said that the UN inspectors need "four days more" to finish their work.

US House of Representatives Speaker John Boehner on Wednesday joined some of his peers by sending a letter to Obama, calling on the president to make his case for launching military strikes on Syria in response to the gas attack.

The top lawmaker demanded that Obama "make the case to the American people and Congress for how potential military action will secure American national security interests, preserve America's credibility, deter the future use of chemical weapons, and, critically, be a part of our broader policy and strategy."

"I think it's important that if, we make a choice to have repercussions for the use of chemical weapons, then the Assad regime, which is involved in a civil war, trying to protect itself, will have received a pretty strong signal, that in fact, it better not do it again," Obama told the PBS.

Obama pledged a "limited, tailored approach" that will not draw the United States into the conflict, saying direct military engagement "would not help the situation on the ground."

"If we are saying in a clear and decisive but very limited way, we send a shot across the bow saying, 'Stop doing this,' this can have a positive impact on our national security over the long term," Obama said.

US media reported that the military strikes under consideration will hit targets inside Syria, involving sea-launched cruise missiles or possibly long-range bombers.

Administration officials said the options aim not at toppling the Syrian government led by President Bashar al-Assad, but rather a direct response to the use of sarin gas last week.

The Syrian government and opposition, engaged in conflict since March 2011, have been blaming each other for the alleged use of the chemical weapons.

An assessment on Syrian government's culpability is expected to be released by the American intelligence later this week.

"When you start talking about chemical weapons in a country that has the largest stockpile of chemical weapons in the world, where over time, their control over chemical weapons may erode, where they're allied to known terrorist organizations that, in the past, have targeted the United States, then there is a prospect, a possibility, in which chemical weapons that can have devastating effects could be directed at us," Obama said. "And we want to make sure that that does not happen."