EMERGING MARKETS-Currencies gain as Turkish lira firms before rate decision

* Turkish central bank expected to keep rates unchanged

* Russia's rouble gains 0.5 percent, oil rises

* MSCI's EM stocks index hits six-week peak

* S.African rand firmer ahead of local retail sales data

Jan 16 (Reuters) - Most emerging market currencies firmed against the dollar on Wednesday, with Turkey's lira strengthening ahead of a central bank rate decision, while stocks in the developing world notched a six-week peak.

Turkey's central bank sets borrowing costs later in the day, with a Reuters poll predicting the key rate will remain at a formidable 24 percent despite moderating inflation.

The lira was 0.8 percent firmer after hitting its strongest level against the dollar in more than a week.

Tim Ash, emerging markets senior sovereign strategist at BlueBay Asset Management, said he did not think the bank would be "that naïve as to pre-emptively cut rates at this stage".

A diplomatic row with the United States, a spike in oil prices to multi-year peaks and doubts investors had about the central bank's independence hammered the lira in 2018. It ended the year more than 28 percent weaker, its worst annual showing in 17 years.

"Cutting too early would risk more carnage for the (lira), and putting the currency back into the death spiral which threatened back in the summer - meaning deeper recession, higher inflation, and macro destabilisation," Ash said.

Neither the central bank nor Turkish President Tayyip Erdogan's AKP party would want a repeat of those conditions in the run-up to local elections, he added.

Turkish stocks were up half a percent, aided by gains among financial shares. MSCI's index of emerging market stocks rose 0.2 percent.

A half-percent rise in Russia's rouble was underpinned by an increase in the price of oil, the country's main export.

Gains in Russian stocks were tempered by a drop in the Moscow-listed shares of Rusal after the U.S. Senate voted to advance a resolution disapproving of a Trump administration plan to ease sanctions on Russian firms tied to oligarch Oleg Deripaska.

South Africa's rand was 0.6 percent firmer. Market participants awaited local retail sales data for clues on the health of Africa's most industrialised economy.

South African stocks edged 0.1 percent higher.

Following the parliamentary rejection of British Prime Minister Theresa May's Brexit proposal, currencies softened in central and eastern Europe a region exposed to Brexit ructions. Hungary's forint hit a more than one-month low against the euro.

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For RUSSIAN market report, see (Reporting by Aaron Saldanha in Bengaluru, Additional reporting by Karin Strohecker in London; Editing by Dale Hudson)