Updated

The U.S. and its allies are "bringing pressure to bear" on Syria's government, but will not provide weapons to Syrian rebels trying to get rid of the government led by despotic leader Bashar Assad, President Obama's chief of staff said Sunday.

"The last thing that is needed in Syria now is more violence," Jacob Lew told "Fox News Sunday."

Instead, Lew said the U.S. is working with the Arab League and other partners to bring "serious financial pressure" on Syria. He said Assad's government is "feeling it."

"The transition from tyranny to democracy is very hard. the Syrian people have to handle this in a way that works in Syria. There is no question that this regime will come to an end. The only question is when," he added.

But Sen. Joe Lieberman, D-Conn., said Assad has become emboldened since China and Russia vetoed a U.N. Security Council resolution aimed at creating a peace plan for Syria that would include Assad's removal.

Lieberman said arming the Syrian rebels would not only help them get a leg up on Assad, whose army is being aided by Iran and Russia, but would lead to a defeat, which would be "a great moral and democratic victory for the people of Syria and a great strategic defeat for the fanatical regime in Iran."

"This is a moment when every option with regard to Syria should be on the table except for doing nothing," he said, adding that the Syrian rebels "are fighting valiantly against this tyrant, but they need our help."

With a meeting of the Arab League in Cairo on Sunday, Lieberman said he hoped the group, along with the United States and European nations would provide Syrian rebels medical help, communications equipment, intelligence and more.

"I would say it's time to give weapons to the Syrian freedom fighters against Assad. ... It's not a fair fight now, the rest of the world has to give arms to the Syrians, the people so they can fight this dictator and get rid of (him)."

Arming Syrian rebels is fraught with potential consequence, particularly as al Qaeda-linked fighters are said to be entering the country from northern Iraq to help the rebels. On Saturday, al Qaeda leader Ayman Al-Zawahiri, who took over after Usama bin Laden's death, released a videotaped statement telling Muslims in Syria's neighboring states to rise up against Assad and not rely on the West or its allies like Turkey to rid the country of the "pernicious, cancerous regime."