U.S. Secretary of State Hillary Clinton is in Libya for a previously unannounced visit with the country's new rulers, while Libyan provisional government fighters launched an assault on the last remaining stronghold of former leader Moammar Gadhafi.

Clinton arrived Tuesday in the capital of Tripoli, where she pledged millions of dollars in new aid for educational programs and medical care for wounded fighters. She said more money will go toward securing stockpiles of weapons from Mr. Gadhafi's rule and destroying chemical weapon stocks.

U.S. officials say American aid to Libya since the conflict began totals $135 million.

Clinton met with interim prime minister Mahmoud Jibril and National Transitional Council chairman Mustafa Abdel Jalil during her visit. She is the most senior U.S. official to visit Tripoli since the uprising against Mr. Gadhafi began in February.

In a news conference with Mr. Jibril Tuesday, Clinton said it was an honor to stand on the soil of a “free Libya” and a privilege to see a “new future for Libya being born.”

She later met with students and society leaders at a university in Tripoli, where she said the U.S. wants to see the former Libyan leader “killed or captured” soon.

Meanwhile, hundreds of Libyan government fighters on Tuesday carried out an attack on the coastal city of Sirte, a day after saying they captured Bani Walid, the only other remaining Gadhafi loyalist stronghold.

Pro-Gadhafi fighters have been hemmed into a small area of Sirte, where National Transitional Council forces have tried for weeks to gain control. NTC officials have said capturing Mr. Gadhafi's hometown would allow them to declare their country liberated.

On Monday, NTC officials said the desert town of Bani Walid was completely free of pro-Gadhafi fighters. Provisional government forces had launched a new assault Sunday on the town, about 170 kilometers southeast of Tripoli.