Updated 3:15 PM ET
The Obama administration is getting ready to tighten its ties to Syria's main opposition group, a step in the intensifying diplomacy that officials hope will craft an end to Syrian President Bashar Assad's embattled regime.
Officials say the administration is on track to recognize the new Syrian opposition council as the sole legitimate representative of the Syrian people at an international conference on the crisis in Morocco this week.
The move will pave the way for greater U.S. support for those seeking to oust Assad and follows the blacklisting of a militant Syrian rebel group with links to al Qaeda. That step is aimed at blunting the influence of extremists amid fears that the regime may use or lose control of its stockpile of chemical weapons.
Defense Secretary Leon Panetta said Tuesday that intelligence suggesting the Syrian government was preparing for the possible use of chemical weapons against rebel forces had "leveled off."
Last week, U.S. officials said there was evidence that Syrian forces had begun preparing sarin, a nerve agent, for possible use in bombs.
"We haven't seen anything new indicating any aggressive steps to move forward in that way," Panetta told reporters traveling with him to Kuwait, where he will visit U.S. troops at the start of a four-day trip.
Secretary of State Hillary Rodham Clinton had been due to attend Wednesday's meeting in the Moroccan city of Marrakech but canceled her trip because she was ill with a stomach virus, her spokesman, Philippe Reines, said. Instead, Deputy Secretary of State William Burns will lead the U.S. delegation.
On Monday, Clinton designated Jabhat al-Nusra, or "the Support Front" in Arabic, a foreign terrorist organization. The move freezes any assets its members may have in U.S. jurisdictions and bars Americans from providing the group with material support. The designation is largely symbolic because the group is not thought to have holdings or support in the United States, but officials hope the penalties will encourage others to take similar action and discourage Syrians from joining.
That step was part of a package intended to help the leadership of the newly formed Syrian Opposition Council improve its standing and credibility as it pushes ahead with planning for a post-Assad future.
Designating al-Nusra a terrorist organization was not a move without risks, however.
CBS News correspondentthat al Nusra is an offshoot of al Qaeda in Iraq, which once fought a no-holds-barred battle against American troops. According to Jeffrey White, a former analyst for the Defense Intelligence Agency, they are now turning the tide against the Assad regime.
"They are very good fighters. They give the rebels a combat edge. They're quite willing to die. They fight on all the key fronts. They're involved in many of the key actions, many of the successful actions of the rebels. These are not people that we want to win," White said.
CBS News correspondent Clarissa Ward says many in the Syrian opposition credit al-Nusra with giving the rebels the focus they lacked a year ago, and many on the ground will see the designation of al-Nusra as a terrorist organization as further evidence that America is secretly supporting Assad.
"There is a sense of anger that the U.S. has not helped the Syrian opposition, and now is going one step further by punishing the people who actually are helping," says Ward, who last snuck into Syria to report for CBS News in October.
Yaser Tabbara, spokesman and legal advisor to the Syrian Opposition Council, said about the designation of al-Nusra: "There's been some frustration at the American designation, that it might not be helpful, and that perhaps there should have been a more nuanced approach.
"We will work with everyone on the ground who has the agenda of ending the suffering of the Syrian people. However, those extremist people with extreme views that are not in line with the general principles -- first, there will be attempts at dialogue. If not, there will be isolation of them."
Opposition supporters were quick to voice their anger online Tuesday.
"It wouldn't be so bad if the U.S. has actually helped in any way but given that they haven't they should butt out," said Shakeeb Al-Jabri on Twitter.
In a higher-level indication of how potentially problematic the designation of al-Nusra could prove, the recently-named leader of the Syrian opposition coalition the U.S. is expected to officially recognize this week strongly implied to CBS News that he did not see a reason for the move. Mouaz al-Khatib did not, however, condemn the U.S. move.
The upgraded status for al-Khatib's council that the U.S. is preparing to announce in Marrakech will be the more significant move, diplomatically. It is expected to be accompanied by pledges of additional humanitarian and nonlethal logistical support for the opposition. It's unlikely that the U.S. would add military assistance to that, at least in the short-term. Providing arms remains a matter of intense internal debate inside the administration, officials said.
Recognition of the council as the sole representative of Syria's diverse population will bring the United States into line with Britain, France and several of America's Arab allies, which took the same step shortly after the body was created at a meeting of opposition representatives in Qatar last month.
The U.S. had been leading international efforts to prod the fractured Syrian opposition into coalescing around a leadership that would truly represent all of the country's factions and religions. Yet it had held back from granting recognition to the group until it demonstrated that it could organize itself in credible fashion.
In particular, Washington had wanted to see the group set up smaller committees that could deal with specific immediate and short-term issues, such as governing currently liberated parts of Syria and putting in place institutions to address the needs of people once Assad is ousted. Some of those committees could form the basis of a transitional government.
Officials said the U.S. evolution in recognizing Syria's opposition would closely mirror the process the administration took last year in Libya with its opposition.
"I would remind you of how this went in the Libya context where we were able to take progressive steps as the Libyan opposition themselves took steps to work with them, and to advance the way we dealt with them politically," State Department spokeswoman Victoria Nuland said Monday.
In that case, Libya's National Transitional Council moved from being "a" legitimate representative to "the" legitimate representative of the Libyan people. While the revolution was still going on, the council then opened an office in Washington, and the administration sent the late Ambassador Chris Stevens to Benghazi, Libya, as an envoy in return. The move also opened the door for Libya's new leaders to access billions of dollars in assets frozen in U.S. banks that had belonged to the Qaddafi regime.
The move could allow the Syrian opposition to set up a liaison office in Washington with a de facto ambassador.
It is unclear, however, given the level of violence in Syria and the potential threat of chemical weapons, if the U.S. would soon send a representative to rebel-controlled areas of the country.
The conflict started 20 months ago as an uprising against Assad, whose family has ruled the country for four decades. It quickly morphed into a civil war, with rebels taking up arms to fight back against a bloody crackdown by the government. According to activists, at least 40,000 people have been killed since March 2011.