The Obama administration said Friday that Lebanon-based Hezbollah is assisting Syria's domestic military crackdown and it announced new sanctions against the group and the government of President Bashar Assad.

The announcements were timed to precede Secretary of State Hillary Rodham Clinton's meetings Saturday with Syrian opposition leaders in Turkey. Clinton also plans to pledge an additional $5.5 million in U.S. humanitarian aid for Syrian refugees.

The new measures are unlikely to placate Syrian rebel forces that have asked for U.S. military equipment and aerial protection in their increasingly bloody fight against Assad. Nor are they likely to please critics at home who charge President Obama is sitting on the sidelines of a humanitarian crisis and a battle that threatens U.S. security interests in the region, current and former U.S. officials said.

Short of direct U.S. intervention, Clinton plans to discuss other options in sessions with Assad opponents and Turkish government leaders. The one-day stop follows her 10-day trip to Africa.

The cautious U.S. policy could change, as it did last year in Libya, despite the administration's concern that adding weapons to the volatile and increasingly sectarian civil war in Syria would make things worse.

Clinton is looking for a "clear picture of the effectiveness of what we are currently providing and how it can be made more effective, and then whether or not there are additional things we can do," said a State Department official on condition of anonymity.

But skepticism about the utility of any military assistance, a lack of international consensus and the upcoming U.S. presidential election make the possibility of any near-term military operation appear remote.

Amid fears extremists are gaining strength within rebel ranks, some administration officials have argued internally that increased U.S. involvement would improve the likelihood of a democratic outcome and provide greater U.S. influence with the government that eventually replaces Assad. Republican presidential candidate Mitt Romney has said the United States should work with allies who are already supplying weapons to the rebels.

Obama has not ruled out any options in Syria, but administration counterterrorism adviser John Brennan said this week that opposition forces there are already "awash in weaponry." There is little indication a war-weary American public favors intervention in Syria.

The new U.S. sanctions on Hezbollah are likely to have more symbolic than substantive effect. The Syrian regime and Hezbollah, which is on the State Department's list of terrorist groups, already are so isolated internationally that it's unclear what, if any, punitive effect such measures would carry.

Separately, the administration imposed new sanctions on Syria's state-run oil company, Sytrol. Because Syrian government entities are already subject to U.S. sanctions, the action is again primarily symbolic.

Material from McClatchy News Services is included in this report.