* Central bank to watch major currencies in guiding yuan

* Message comes ahead of Obama's China visit

* Analysts say actual change unlikely to be sudden

* For economists' reaction, click on [ID:nSP347101]

By Zhou Xin and Jason Subler

BEIJING, Nov 11 (Reuters) - China sent its clearest signal yet that it was ready to allow yuan appreciation after an 18-month hiatus, saying on Wednesday it would consider major currencies, not just the dollar, in guiding the exchange rate.

In its third-quarter monetary policy report, the People's Bank of China departed from well-worn language on keeping the yuan CNY=CFXS "basically stable at a reasonable and balanced level". It hinted instead at a shift from an effective dollar peg that has been in place since the middle of last year.

"Following the principles of initiative, controllability and gradualism, with reference to international capital flows and changes in major currencies, we will improve the yuan exchange rate formation mechanism," the central bank said in a 46-page monetary policy report.

The comments, published just days before a visit to Shanghai and Beijing by U.S. President Barack Obama, set out the possibility of a return to exchange rate appreciation that began with a landmark July 2005 revaluation.