Citi has forecast a "gradual shift towards helicopter money" by advanced economies, as countries struggle to boost growth and inflation in uncertain geopolitical climes.

The bank's report came as the Bank of Japan started a two-day meeting on Thursday, after which it is widely expected to launch another major stimulus program. Prime Minister Shinzo Abe is seen announcing a fiscal stimulus package as well, which a report by news agency Jiji put at 28 trillion yen ($267 billion).

That could be viewed as a move towards helicopter money, defined by Citi as a "temporary fiscal stimulus financed by a permanent monetary expansion." Others define it simply as central banks injecting cash directly into the real economy.

"Amid large uncertainties, the policy outlook is once again of major importance. In our view, there is a gradual shift in policy orientation towards helicopter money," Citi analysts including Chief Economist Willem Buiter said in a report on Wednesday.

Citi forecasts "moderate further easing" by the Bank of Japan this week and a new round of a quantitative easing from the Bank of England (BoE) next month.