In what could be a turning point in the Libyan uprising, rebel forces closed in on Tripoli, the capital, isolating leader Col. Muammar Gaddafi. Rebel leaders said over the weekend that they had conquered Zawiyah, a crucial city that lies between Tripoli and the Tunisian border, and rebels claimed to have captured two nearby towns on Monday—putting the coastal road to Tripoli within their reach. “If the road is cut off, then Tripoli is slowly going to be strangled to death,” said Libya expert George Joffe. Meanwhile, Gaddafi’s inner circle took a hit Monday when one of his key aides, Interior Minister Nassr al-Mabrouk Abdullah, defected to Cairo. Members of the rebel Transitional National Council met with Gaddafi’s representatives in Tunisia for talks, but Gaddafi denounced NATO in a recording on state television Monday.