  We present high-resolution Very Large Array imaging of the molecular gas in
the host galaxy of the high redshift quasar BRI 1335-0417 (z=4.41). Our CO(2-1)
observations have a linear resolution of 0.15" (1.0 kpc) and resolve the
molecular gas emission both spatially and in velocity. The molecular gas in BRI
1335-0417 is extended on scales of 5 kpc, and shows a complex structure. At
least three distinct components encompassing about two thirds of the total
molecular mass of 9.2 x 10^10 M_sun are identified in velocity space, which are
embedded in a structure that harbors about one third of the total molecular
mass in the system. The brightest CO(2-1) line emission region has a peak
brightness temperature of 61+/-9 K within 1 kpc diameter, which is comparable
to the kinetic gas temperature as predicted from the CO line excitation. This
is also comparable to the gas temperatures found in the central regions of
nearby ultra-luminous infrared galaxies, which are however much more compact
than 1 kpc. The spatial and velocity structure of the molecular reservoir in
BRI 1335-0417 is inconsistent with a simple gravitationally bound disk, but
resembles a merging system. Our observations are consistent with a major,
gas-rich (`wet') merger that both feeds an accreting supermassive black hole
(causing the bright quasar activity), and fuels a massive starburst that builds
up the stellar bulge in this galaxy. Our study of this z>4 quasar host galaxy
may thus be the most direct observational evidence that `wet' mergers at high
redshift are related to AGN activity.
