The Central Bank cut interest rates Friday for the fourth time in more than three months as part of a campaign to encourage commercial banks to kick-start the economy by offering affordable loans.

The rate cut added pressure to an already weakening ruble, which posted its biggest daily fall in half a year. Dealers said the Central Bank might have intervened in the market — selling foreign currency for the first time since late January — in a bid to cap the ruble’s losses.

The benchmark refinancing rate will be reduced by 50 basis points to 11 percent as of Monday, while the minimum one-day repo rate will be cut by the same amount to 8 percent.

“The [Central Bank] expects that this measure will create the necessary conditions for the reduction of loan rates for the end-borrowers and resumption of lending activity,” the regulator said in a statement.

The ruble closed at 38.50 versus a euro-dollar basket, down 2.6 percent, extending earlier losses sparked by oil prices. The ruble has not been that weak since April, when oil was trading at $46.

“It was already on the edge before the rate cut. The rate cut may have just pushed it over the edge,” said a dealer at a foreign bank in Moscow.

Central Bank Chairman Sergei Ignatyev had signaled that the next move on rates could come as soon as July, and in a poll last week economists forecast that the refinancing rate would be cut to 10.50 percent by year-end.

“This is a completely expected decision, and I would count on one or two further cuts by the end of the summer,” said Natalya Orlova, chief economist at Alfa Bank.

The Central Bank has set the ruble’s trading band at 26 to 41 against the basket but reserves the right to intervene within those boundaries to avoid excessive swings.

“There was panic buying [of rubles] after 38 was pierced because there were rumors that [the Central Bank) is there,” said Gazprombank dealer Viktor Kholoshnoi.

Three other dealers agreed that there might have been intervention, with one of them estimating that the Central Bank had sold about $2 billion.

The Central Bank does not comment on its day-to-day currency market operations, but publishes monthly data on interventions.

State-controlled Sberbank this month lowered its loan rates by 100 basis points, passing on some of the Central Bank easing to its clients.

But lower rates do not necessarily mean more loans. Banks remain concerned about the rise in bad loans and the creditworthiness of would-be borrowers — loans to nonfinancial organizations fell 1.5 percent in May.

“Despite the consistent lowering of interest rates … in April-June 2009, the rates for loans to end borrowers remain high,” the Central Bank said.