Updated

President Obama said Monday that the U.S. and its NATO allies are still considering "potential military options" to stop the violence in Libya, warning those in Muammar al-Qaddafi's inner circle that they will be "held accountable" if they continue to stand by the leader's side.

The president addressed the escalating situation in Libya after meeting with Australian Prime Minister Julia Gillard in Washington. Obama said both countries see the violence being perpetrated by the Libyan government as "unacceptable." Obama announced he has authorized an additional $15 million in humanitarian aid as forces loyal to Qaddafi step up their crackdown on the opposition.

The president made clear that military action is still on the table, though he did not offer any details. He said NATO allies in Brussels are considering "a wide range of potential options, including potential military options."

A number of Qaddafi officials have defected since the violence broke out, but Obama sent a message to those continuing to craft and carry out his orders.

"I want to send a very clear message to those who are around Colonel Qaddafi. It is their choice to make how they operate moving forward," he said. "And they will be held accountable for whatever violence continues to take place."

Libyan warplanes launched multiple airstrikes Monday on opposition fighters in the second day of a harsh government crackdown to thwart rebels advancing on Qaddafi's stronghold in Tripoli.

The United States sent an initial $10 million in humanitarian aid to Libya last month. The U.S. and United Nations have imposed sanctions on Qaddafi's regime, and U.S. military forces have also moved closer to Libya's shores to back up demands that Qaddafi step down.

While the administration says the possibility of military action is and has been on the table, some have pushed more forcefully for a no-fly zone to be imposed. Sen. John McCain, R-Ariz., said Friday that doing so would hamstring Qaddafi and "hasten his departure."

But White House Chief of Staff Bill Daley pushed back on those calls Sunday.

"Lots of people throw around phrases of 'no-fly zone' and they talk about it as though it's just a game, a video game or something. Some people who throw that line out have no idea what they're talking about," Daley said.

Hundreds if not thousands of people have died since Libya's uprising began, although tight restrictions on media make it near impossible to get an accurate tally. More than 200,000 people have fled the country, most of them foreign workers, creating a humanitarian crisis across the border with Tunisia -- another North African country in turmoil after an uprising in January that ousted its longtime leader.

The Associated Press contributed to this report.