(Reuters) - Community health centers expect to sign up millions of newly insured patients under President Barack Obama's health reform law, but U.S. budget cuts just as they need to beef up services may make it hard to keep the newcomers. The federally funded centers have been a safety net in the nation's poorest areas since 1965, offering primary care and mental health services to 22 million people, more than a third of them without insurance. When the Affordable Care Act, popularly known as Obamacare, takes full effect on Jan. 1, the 1,200 clinics plan to help enroll many of the newly insured. That campaign is expected to bring 10 million new patients within a year.