The Reserve Bank of New Zealand has held its official cash rate at 2.5 per cent as expected, but has warned once again that it is monitoring the current strong housing inflation closely for risks to financial stability.The bank is preparing a set of macro-prudential tools to cool a surge of high loan-to-valuation ratio lending in the hot Auckland housing market. It is expected to give further details on its concerns, and possible actions, at the May 8 release of its half yearly Financial Stability Report.However, the Reserve Bank's statement on the OCR stopped short of suggesting it would hike up the cash rate to slow the housing market, which it has hinted at in previous statements and in speeches and at news conferences. It also repeated its expectation that the OCR would not change "through [to] the end of 2013."New Zealand economists said the Reserve Bank could afford to wait to hike up the OCR until the first quarter of 2014. The bank is also grappling with a New Zealand dollar which is at a record high. The risk is that a hike in the OCR to slow the housing market would lift the currency even higher, pushing up inflation and depressing the export sector even further."House price inflation is high in some regions, despite prices already being elevated.  The bank does not want to see financial or price stability compromised by housing demand getting too far ahead of supply," Reserve Bank governor Graeme Wheeler said in the short statement. The bank's next full monetary policy statement is not due until June 13.BNZ economist Craig Ebert said: "Its language was a tad more aggressive [in this statement]. Averting a bigger bubble appears [to be] the theme."ANZ economist Cameron Bagrie said the central bank's comment about financial stability being compromised by house price inflation was a "coded warning" the bank was considering a policy response."While the policy assessment did not specifically mention forthcoming changes to prudential policy, recent RBNZ announcements suggest the bank has not been idle," Bagrie said, referring to proposals for higher capital weightings for riskier mortgages.