By Sam Forgione

NEW YORK (Reuters) - The dollar fell against the safe-haven yen on Monday after comments from a top Bank of Japan (BOJ) official reinforced views that the central bank was unable to weaken the yen, while an impending U.S. presidential debate stoked uncertainty.

BOJ Governor Haruhiko Kuroda said Monday the central bank stood ready to use every possible policy tool to achieve its 2-percent inflation target. He also said no big increase or decrease to its bond buying was expected for now.

The comments eased speculation that the BOJ was considering tapering asset purchases and supported a view that the BOJ was keeping in place a monetary policy that has only led the yen to strengthen.

The yen has gained more than 17 percent since the BOJ shocked markets in January by cutting rates below zero for the first time. The dollar was last down 0.7 percent against the yen <JPY=> at 100.29 yen after touching a session low of 100.25 yen.

"When Kuroda speaks and he doesn’t explicitly acknowledge that the BOJ needs a higher (quantitative easing) quantity, the yen strengthens," said Greg Anderson, global head of FX strategy at BMO Capital Markets in New York, in reference to the quantity of bonds that the central bank is buying as part of its stimulus effort.

The yen also gained ahead of a U.S. presidential debate between Democrat Hillary Clinton and Republican Donald Trump at 9 p.m. ET (0100 GMT on Tuesday), as well as Moody's move to cut Turkey's sovereign rating to "junk" on Friday and an uncertain outcome to an OPEC meeting.

Analysts said uncertainty over the impact of the U.S. presidential debate hurt the dollar. The dollar index <.DXY>, which measures the greenback against a basket of six major currencies, was last down 0.2 percent at 95.300.

"Most market participants are waiting to see what comes out of the debate tonight and will take their cue from there," said Richard Scalone, co-head of foreign exchange at TJM Brokerage in Chicago.

The euro was last up 0.3 percent against the dollar at $1.1252 after hitting an 11-day high of $1.1278 earlier in the U.S. trading session.

The dollar was last up 0.5 percent against the Turkish lira <TRY=> at $2.9813 liras in the wake of the Turkey credit downgrade after hitting a seven-week high against the lira in early trade of $2.9981.

(Editing by Bernadette Baum and Nick Zieminski)