JOHANNESBURG (Reuters) - Ratings firm Moody's will visit South Africa in the next week to decide whether to downgrade its credit status to just one notch above sub-investment grade, the Treasury said on Wednesday. "This review visit will primarily serve to either affirm the current ratings or downgrade them," it said in a statement. On Tuesday, Moody's said it was placing South Africa's Baa2 ratings on review for downgrade, citing the economy's weak growth prospects and the government's worsening fiscal position. [nFWN16G023] (Reporting by Mfuneko Toyana; Editing by Ed Cropley)