The high resolution absorption spectrum of methane has been recorded at room temperature by high sensitivity CW-cavity ring down spectroscopy between 1.50 and 1.60 mu m (6250-6680 cm(-1)). This spectral region has a low opacity and is then of particular interest for the spectral analysis of the outer planets and Titan. The recordings were performed with a sensitivity corresponding to a noise equivalent absorption of alpha(min) similar to 5 x 10(-10) cm(-1) and allowed for the detection of lines with an intensity smaller than 10(-28) cm/molecule far beyond the weakest lines provided by the HITRAN database. The spectrum exhibits a highly complex and congested structure with a kind of 'fractal' character and a density of transitions of a few tens per cm-1. The impact of the weak newly observed transitions on the total absorption in the region is discussed. (c) 2007 Elsevier B.V. All rights reserved.