President Obama on Tuesday authorized $25 million in non-lethal assistance to the Libyan opposition -- the first direct U.S. aid to the rebels after weeks of assessing their capabilities and intentions.

In a memo to the State Department and the Pentagon, Obama said he is using his so-called "drawdown authority" to give the opposition, led by the Transitional National Council in Benghazi, up to $25 million in surplus American goods to help protect civilians in rebel-held areas threatened by Libyan leader Muammar al-Qaddafi's forces.

This falls short of providing military aid and weapons to the rebels, which some U.S. lawmakers have urged, most notably Arizona Sen. John McCain.

The U.S. and it's allies already have provided firepower in the form of airstrikes on Qaddafi defense sites as part of a U.N.-authorized no-fly zone intended to stop attacks on civilians. But the Obama administration has declined so far to pledge direct military aid to the rebels, as some have raised concerns about possible ties to terror groups.

The pledge of non-lethal aid includes medical supplies, uniforms, boots, tents, personal protective gear, radios and Halal meals, which are meals prepared according to Islamic tradition. But the money may not be used to offer Libyan rebels broader assistance, including cash, weapons or ammunition.

At the same time, the Obama administration has eased its sanctions against Libya to allow for the sale of oil controlled by the rebels. That move will allow Libya's opposition forces to use the income from oil sales to buy weapons and other supplies.

The U.S. Treasury Department's Office of Foreign Assets Control issued the order Tuesday. It will allow U.S. companies to engage in transactions involving oil, natural gas and other petroleum products if the petroleum exports will benefit the opposition Transitional National Council of Libya.

The new order modified sanctions the administration had imposed in February freezing $34 billion in assets held by Qaddafi, his family members and top government officials. The original order had imposed sanctions on Libya's oil companies.

Libyan government forces on Tuesday bombarded the port of Misrata, in a virtually nonstop assault on the sole lifeline of a battered population that has been under siege for the past two months.

While forces loyal to Qaddafi pulled out of the city over the weekend under pressure from NATO airstrikes, they have since unleashed a withering rocket and mortar barrage on Misrata that has killed dozens. The bombardment Tuesday was constant throughout the afternoon and into the evening, and loud explosions could be heard thundering across the city.

The Associated Press contributed to this report.