JOHANNESBURG (Reuters) - South Africa's Finance Minister Pravin Gordhan told Talk Radio 702 on Friday the country would have to limit "political noise" and focus on growing the economy in order to avoid ratings downgrades to junk. Ratings agency Fitch affirmed South Africa's investment grade credit rating at one notch above 'junk' on Friday but changed the outlook to negative from stable, warning that political risks could hurt growth. South Africa has been mired in political wrangles this year, most recently after an anti-graft watchdog alleged influence-peddling in President Jacob Zuma's government. Zuma has denied any wrongdoing. (Reporting by Mfuneko Toyana; Editing by James Macharia)