(Recasts with fresh lows, adds quotes, background)
By Toni Vorobyova
MOSCOW, Jan 28 (Reuters) - The Russian rouble sank to historic lows versus the euro and the dollar on Wednesday as the end of major corporate tax payments freed up speculators to try and test the central bank's new currency boundaries.
On Wednesday the rouble fell by a record 2.5 percent to 38.75 -- its weakest since the current basket compositions was set at 0.45 euros and 0.55 dollars in 2007.
Russia defined the rouble corridor versus a euro-dollar basket last week in a bid to cap a steady devaluation that has knocked a fifth off the rouble's value since November to adjust to weak oil prices and the worst economic outlook in a decade.
Keeping the rouble's depreciation gradual has cost Russia some $200 billion, or a third of its reserves, and not all analysts are convinced the central bank will be able to defend the currency's new boundaries without huge extra expense.
Dealers said the rouble had drawn support from companies needing cash in the local currency to make tax payments.
But with most duties now paid, rouble liquidity remains strained in a sign that people, companies, and banks are not yet convinced it has found its floor and prefer to keep money in foreign currency.
The new trading boundaries of 26 to 41 against the basket allow scope for depreciation of a further 5.5 percent.
"The central bank was believed (about the new boundaries) but look at the levels -- there is still two roubles to go and we need to grab them. We will aim for that. We won't get to 41 today, but by early next week we will definitely see it," said a dealer at a European bank in Moscow.
The rouble hit a record low of 45 per euro, and weakened to 33.80 versus the dollar -- its lowest since Russia began to open up its markets to the world in 1990s.
"As soon as the tax payments finished market participants went back to their old game, pushing the rouble exchange rate lower," said Gintaras Shlizhyus, analyst at RZB.
"In the current situation the central bank has two choices. The first is to let the rouble push to 41 and to try and halt it there with interventions...(But) I think the most sensible choice would be to let the rouble float freely."
TO FLOAT OR NOT?
A free-float of the rouble is Russia's medium-term goal. But risking a big one-off depreciation is a thorny political issue as Russians are all too mindful of the 1998 financial crisis, when the rouble lost over two-thirds of its value in a year.
Proponents of the free-float argue that this time most people and companies have had plenty of time to convert their savings, and that such a currency policy would stop Russia using up all of its reserves in a battle against market speculators.
Others however point out that the rouble is now not far off fair value levels and that the central bank still has plenty of cash to keep exchange rate moves ordered.
German Gref, former economy minister and now CEO of Russia's largest lender Sberbank told Vesti television channel on Wednesday that he thought the bulk of the rouble depreciation was over and current pressure was speculative.
Goldman Sachs economist Rory MacFarquhar broadly agreed.
"Despite the deterioration in the economic outlook -- which in our view was exacerbated over the past two months by the capital outflow resulting from the central bank's gradual depreciation policy -- we continue to believe that the rouble has now reached a sustainable level," he said in a client note.
"We believe that the central bank is committed to the new 26-41 band against the...basket, and that it has plenty of resources to defend the currency."
Russia has around $175 billion left to spend on defending the rouble if you deduct government funds -- including those needed to plug the budget deficit -- from current reserves.