The United States and Libyan rebels have rejected a new offer from the regime of Col. Muammar Gaddafi as the conflict in Libya enters its fifth month. Gaddafi’s son, Saif al-Islam, had said his father would hold elections within three months and would step down if he lost. But the Obama administration rejected the proposal, calling it "too late." NATO warplanes have resumed bombing Tripoli as rebels attempt to advance on the Libyan capital. The rebels say at least 16 of their fighters were killed Thursday in what appears to be an errant NATO air strike. NATO Secretary General Anders Fogh Rasmussen said the international attack on Libya is weakening the Gaddafi regime.