TRIPOLI/SIRTE, Libya - US Secretary of State Hillary Clinton arrived in Libya on Tuesday to meet the new leaders Washington helped into power, while die-hard forces loyal to Muammar Gaddafi launched a surprise counter-attack in his hometown of Sirte. The visit by Clinton, the most senior U.S. official to come to Tripoli since Gaddafi's 42-year rule ended in August, was marked by tight security, reflecting worries that the new rulers have yet to establish full control over the country. US officials said Clinton's visit was aimed at cementing a partnership with the new government and helping it steer towards democracy. Clinton would encourage the National Transitional Council to fulfill pledges to move swiftly towards elections. "The important thing is to be able to show the Libyan people that there is momentum," a senior administration official traveling with Clinton said. "We're pushing the (NTC) to be able to show the Libyan people that they're serious in their commitments to transition, that they're serious in their commitments to rule of law, that they're serious about getting to those elections." Washington is also offering Libya practical help to contain the thousands of weapons flooding the country in the wake of the war to oust Gaddafi. Security experts say these could fall into the hands of al Qaeda. The United States took part in the NATO bombing campaign that helped the NTC take power, although its aircraft largely played a secondary role to those of Britain and France. Nearly two months since capturing Tripoli, the NTC has failed to defeat remaining Gaddafi loyalists, raising questions about its ability to exert its authority over the entire country and postponing the launch of its promised democracy programme. Clinton arrived as the interim government was facing a military setback in Sirte, a city on the Mediterranean coast where a few days ago it was poised to declare victory over pro-Gaddafi forces. Sirte is now the last major Libyan town where pro-Gaddafi forces are holding out, after the other bastion of resistance, Bani Walid, fell to the country's new rulers on Monday. Gaddafi loyalists who had been cornered in a an area of Sirte of about two square kilometres (a square mile) appeared to have broken out of their encirclement, Reuters reporters in the city said. A group of NTC fighters was forced to pull back about 2 km (1.2 miles) after they came under heavy fire. The force was trying to regroup near the Ouagadougou conference centre – the complex where Gaddafi used to host foreign heads of state but was pinned down. A volley of 22 mm rounds from Gaddafi loyalists thudded into the group, hitting four vehicles and seriously wounding one NTC fighter. He was loaded into an ambulance and driven away. On the southern outskirts of the city, in an area that in previous days had been safe from gunfire, mortars were landing and air-burst rounds were exploding overhead. On the edge of the "Seven hundred" district in central Sirte, the front line had not moved but the mood of optimism among NTC fighters had been replaced by despair at the mounting casualties.