HOUSTON — Brian Ching is expected to be sidelined for four-to-six weeks because of a strained left hamstring, an injury that could prevent him from returning to the field before the U.S. World Cup team gathers in mid-May.

The Houston Dynamo forward was injured in last Thursday's home opener. Dynamo spokesman Lester Gretsch said Tuesday that Ching had an MRI a day earlier that revealed the strain and led to the prognonis.

A 31-year-old from Haleiwa and Kamehameha School, Ching was a member of the 2006 U.S. World Cup team and has 11 goals in 44 international appearances.

Ching and Colorado's Conor Casey have been competing to make the 23-man roster.