House Intelligence Committee Chairman Rep. Mike Rogers, R-Mich., walks to a meeting on Capitol Hill in Washington as he and national intelligence advisers prepare to update House members on Syria's alleged use of poisonous gas in its ongoing civil war in this April 26, 2013, file photo. On a talk show Sunday, April 28, 2013, Rogers said he's worried about chemical weapons in Syria falling into the wrong hands after President Bashar Assad is driven from power.

WASHINGTON - Syria's stockpile of chemical weapons could be a greater threat after that nation's president leaves power and could end up targeting Americans at home, lawmakers warned Sunday as they considered a U.S. response that stops short of sending military forces there.

U.S. officials last week declared that the Syrian government probably had used chemical weapons twice in March, newly provocative acts in the 2-year civil war that has killed more than 70,000 people and displaced hundreds of thousands more. The U.S. assessment followed similar conclusions from Britain, France, Israel and Qatar - key allies eager for a more aggressive response to the Syrian conflict.

President Barack Obama has said Syria's likely action - or the transfer of President Bashar Assad's stockpiles to terrorists - would cross a "red line" that would compel the United States to act.

Lawmakers sought to remind viewers on Sunday news programs of Obama's declaration while discouraging a U.S. foothold on the ground there.

"The president has laid down the line, and it can't be a dotted line. It can't be anything other than a red line," said House Intelligence Committee Chairman Rep. Mike Rogers, R-Mich. "And more than just Syria, Iran is paying attention to this. North Korea is paying attention to this."

Added Sen. Saxby Chambliss, R-Ga.: "For America to sit on the sidelines and do nothing is a huge mistake."

Obama has insisted that any use of chemical weapons would change his thinking about the United States' role in Syria but said he didn't have enough information to order aggressive action.

"For the Syrian government to utilize chemical weapons on its people crosses a line that will change my calculus and how the United States approaches these issues," Obama said Friday.

But Rep. Jan Schakowsky, an Illinois Democrat, said Sunday the United States needs to consider those weapons. She said that when Assad leaves power, his opponents could have access to those weapons or they could fall into the hands of U.S. enemies.

"The day after Assad is the day that these chemical weapons could be at risk ... (and) we could be in bigger, even bigger trouble," she said.

Both sides of the civil war already accuse each other of using the chemical weapons.

The deadliest such alleged attack was in the Khan al-Assal village in the Aleppo province in March. The Syrian government called for the United Nations to investigate alleged chemical weapons use by rebels in the attack that killed 31 people.

Syria, however, has not allowed a team of experts into the country because it wants the investigation limited to the single Khan al-Assal incident, while U.N. Secretary-General Ban Ki-moon has urged "immediate and unfettered access" for an expanded investigation.

One of Obama's chief antagonists on Syria, Sen. John McCain, R- Ariz., said the United States should go to Syria as part of an international force to safeguard the chemical weapons. But McCain added that he is not advocating sending ground troops to the nation.

"The worst thing the United States could do right now is put boots on the ground on Syria. That would turn the people against us," McCain said.

His friend, Sen. Lindsey Graham, R-S.C., also said the United States could safeguard the weapons without a ground force. But he cautioned the weapons must be protected for fear that Americans could be targeted. Raising the specter of the lethal bomb at the finish line of the Boston Marathon, Graham said the next attack on U.S. soil could employ weapons that were once part of Assad's arsenal.

"Chemical weapons - enough to kill millions of people - are going to be compromised and fall into the wrong hands, and the next bomb that goes off in America may not have nails and glass in it," he said.

Rogers and Schakowsky spoke to ABC's "This Week." Chambliss and Graham were interviewed on CBS's "Face the Nation." McCain appeared on NBC's "Meet the Press."