Mo Farah faces a testing head-to-head with top American Alan Webb in the Carlsbad 5,000 metres road race on April 6.

The European 5,000m silver-medallist has accepted an invitation to compete at the California venue - even though he is carefully choosing his competitions in Olympic year.

Farah remains adamant nothing must interfere with his preparations for Beijing, which currently are going well after injury problems.

A hamstring problem prevented him defending his European Cross Country title last December - and he is also an absentee from this Sunday's World Cross Country Championships.