We investigate the focusing, that is, the reversing of spreading of continuum wave packets created with chirped laser pulses in the weak-field limit. Focusing can be accomplished when a negative position-momentum correlation is created in the wave packet. Specializing to constant and linear (repulsive) potentials, we show analytically that in a constant potential wave packet spreading can be compensated with positively chirped laser pulses, whereas in the linear potential negatively chirped laser pulses are required, in the short-pulse limit. The analytical results for the linear potential are supported by numerical simulations. The results are discussed in the context of a classical model for wave packet focusing.