WASHINGTON (Reuters) -U.S. job growth picked up in February, but cracks are emerging in the once-resilient labor market amid rising uncertainty over trade policy and deep federal government spending cuts that could undercut economic growth this year. The Labor Department's closely watched employment report on Friday, the first under President Donald Trump's watch, also showed the unemployment rising to 4.1% last month and an increase in the ranks of part-time workers. Economists said the Trump administration's whiplash trade policy was making it difficult for businesses to plan ahead.