The formation of stars begins with the collapse of a dense interstellar cloud core to a protostar surrounded by a disk of gas and dust. Material in the envelope of the cloud core falls inwards to feed further growth of the protostar and its accretion disk. At some point during the accretion phase, an outflow of gas begins along the disk＇s rotation axis. Outflows have been studied in a large number of sources＇, and recently it has become possible to study infall land outflow) very close to the star(2-8). But the possible interaction between these flows and its effect on the mass of the disk and the young star remain uncertain. Here we present observational evidence for an interaction between infalling and outflowing molecular gas. The opening angle of the outflow cone is largest near the star, indicating a widening of the outflow with time. Outside the lobes of the outflowing gas we see a narrow, disk-like region that is infalling. We suggest that the widening of the outflow may isolate the disk from further infall.