At least 22 governors, including four Republicans, support an expansion of Medicaid under President Barack Obama's healthcare reform law, while others are expected to decide in the coming weeks, experts said on Wednesday.

An analysis published by the New England Journal of Medicine said the headcount, which includes 13 Republican governors who staunchly oppose Medicaid expansion, portends an uneven start for "Obamacare" when its most sweeping reform provisions begin on January 1, 2014.

"No clear consensus has emerged," said the authors of the article, Harvard physicians Benjamin Sommers and Arnold Epstein. "It now appears that the (law's) 2014 coverage expansion will have large unintended gaps, as low-income adults in at least a dozen states remain ineligible for any kind of public subsidy for health insurance."