* Russia key rate held at 11 pct
* C.bank worsens macro forecasts
* Inflation, rouble weakness concerns for c.bank
* Reserve replenishment suspended if oil at $50 (Adds details, comments, new c.bank forecasts)
By Jason Bush, Lidia Kelly and Alexander Winning
MOSCOW, Sept 11 (Reuters) - The Russian central bank left its main lending rate on hold as expected on Friday, for now putting concerns about stubbornly high inflation before worries about a slumping economy.
The bank left its policy rate unchanged at 11 percent, following five successive cuts this year that have reduced the rate by six percentage points after an emergency hike to 17 percent last December.
The decision to hold rates steady underscores the harsh policy dilemmas facing Russia as it simultaneously grapples with rising double-digit inflation and an economy in the throes of its deepest slump since 2009.
Analysts had widely anticipated Friday's decision following a slide in the rouble over recent weeks that is adding to inflation, and expectations the U.S. Federal Reserve will raise its own rates, perhaps as early as next week.
In an accompanying statement and a three-year monetary policy strategy document also published on Friday, the bank painted a gloomy picture of economic prospects for the years ahead.
"It's important to understand that even in the best case, in the optimistic scenario, the Russian economy in the next few years will function in more difficult external conditions than before and will come up against complex challenges," central bank Governor Elvira Nabiullina said at a press conference after the meeting.
The bank predicted that oil prices would remain around $50 per barrel for at least the next three years, and saw annual gross domestic product returning to growth only in 2017.
It forecast GDP would decline by 3.9-4.4 percent in 2015 and by 0.5-1 percent in 2016, revising down previous forecasts.
"I would highlight the realism and pessimism of the statement, especially on growth," said Christopher Granville, managing director of London consultancy Trusted Sources.
The bank explained its decision to hold, notwithstanding the miserable growth outlook, by saying inflation and inflation expectations had been showing a clear upward trend because of the weaker rouble.
"Our take from the CBR comment is that the policy rate will remain frozen at 11 percent until at least the end of this year, and probably even later unless the situation on the global markets improves," Alfa Bank economist Natalia Orlova said in note.
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