The Bank of Japan said it will buy Japanese real estate investment trusts with credit ratings of AA or higher, providing more details on how it will invest money in a new fund that aims to stimulate demand and defeat deflation.

The central bank will also buy exchange-traded funds that track the Nikkei 225 stock average and the Topix index, the BOJ said in a statement after its Policy Board decided Friday to leave unchanged its key interest rate and cash provision targets. It brought forward the two-day gathering by more than a week so it could complete details about the ¥5 trillion fund unveiled last month that will also buy government and corporate debt.

Coming two days after the Federal Reserve's decision to pour $600 billion into the U.S. market to support growth, the BOJ's inaction on policy underscores its relief that the U.S. move didn't lead to a yen surge. Should the currency's rise resume and threaten exporters in the coming months, BOJ Gov. Masaaki Shirakawa may be forced to boost the asset fund, said economist Takehiro Sato.

"The size of the fund is becoming a sort of new policy target for the BOJ's monetary policy easing," said Sato, chief Japan economist at Morgan Stanley MUFG Securities Co. in Tokyo. "The governor himself has already flagged his readiness to expand the fund."

The BOJ Policy Board voted unanimously to keep the overnight call rate between zero and 0.1 percent. It also maintained the sizes of its ¥5 trillion fund and a ¥30 trillion program to encourage bank lending.

All 16 economists surveyed after the Fed decision said they didn't expect the BOJ to follow the U.S. move with additional monetary stimulus Friday.

"A sense of relief is probably spreading among BOJ policymakers for now because a big yen jump has been avoided," said Jun Ishii, chief fixed-income strategist at Mitsubishi UFJ Morgan Stanley in Tokyo. Even so, "the governor will probably keep underlining that the expansion of the fund is a probable option for the BOJ."

The yen has strengthened 0.4 percent against the dollar since the Fed move on Nov. 3.

The BOJ plans to buy ¥3.5 trillion in government debt, ¥500 billion each of corporate bonds and commercial paper, ¥450 billion in exchange-traded funds and ¥50 billion for real-estate investment trusts. The bank will buy these assets over a year.

It will purchase J-REITs that have a trading record of more than 200 days a year and total value of more than ¥20 billion per annum, the BOJ said in a statement. The bank will start buying government debt early next week.

Shirakawa on Thursday called the asset-purchase fund an "unprecedented" and "extraordinary" step for a central bank, aimed at pushing down borrowing costs further.

"There's about a 13 times difference in the amount of risk when comparing buying five-year U.S. Treasuries to ETF," he said.

The BOJ said Friday the "recovery seems to be pausing," a more pessimistic assessment than in October, when it said the pace of the economic rebound is "slowing down."

The BOJ program falls short of what's needed to end deflation and alleviate the damage from the yen's climb to a 15-year high against the dollar, economists from Citigroup Inc. to Morgan Stanley have said.

Asset purchases of ¥100 trillion "would be more appropriate," Citigroup Chief Economist Willem Buiter and analysts including Tokyo-based Kiichi Murashima said last week. The BOJ may need to ease policy further in the January-March period, when slower inflation in the U.S. could prompt the Fed to buy more government bonds, Murashima said.

A strong yen threatens to depress Japan's already weakening economic expansion by eroding profits of exporters such as Nissan Motor Co. and Sony Corp. and worsening deflation.

BOJ policymakers last week forecast consumer price growth of 0.1 percent in the fiscal year starting next April, and predicted a 0.6 percent increase the following year. Both projections are below the 1 percent price increase that board members consider representing price stability.

Government reports last week suggested that an appreciating currency and decreasing overseas demand for Japanese products are causing the nation's economy to lose momentum. Factory production slumped by more than double the pace economists forecast and deflation deepened in September.