Rostro-caudal patterning of vertebrates depends on the temporally progressive activation of <i>HOX</i> genes within axial stem cells that fuel axial embryo elongation. Whether <i>HOX</i> genes sequential activation, the “<i>HOX</i> clock”, is paced by intrinsic chromatin-based timing mechanisms or by temporal changes in extrinsic cues remains unclear. Here, we studied <i>HOX</i> clock pacing in human pluripotent stem cells differentiating into spinal cord motor neuron subtypes which are progenies of axial progenitors. We show that the progressive activation of caudal <i>HOX</i> genes in axial progenitors is controlled by a dynamic increase in FGF signaling. Blocking FGF pathway stalled induction of <i>HOX</i> genes, while precocious increase in FGF alone, or with GDF11 ligand, accelerated the <i>HOX</i> clock. Cells differentiated under accelerated <i>HOX</i> induction generated appropriate posterior motor neuron subtypes found along the human embryonic spinal cord. The <i>HOX</i> clock is thus dynamically paced by exposure parameters to secreted cues. Its manipulation by extrinsic factors alleviates temporal requirements to provide unprecedented synchronized access to human cells of multiple, defined, rostro-caudal identities for basic and translational applications.