The dollar slid to its weakest against the in more than three months on Monday as expectations of higher U.S. interest rates faded.
The yen's break past 101 yen per dollar was the first time since November that it has traded stronger than its 200-day moving average. In nominal terms, it is the strongest since early February. That reflected both a dip in U.S. treasury yields in the past week and the dollar's broader failure to deliver the strength many had expected this year.
But dealers said there were options barriers around 101 and talk of official buyers in Japan around 100 yen. That will block any further push before a two-day meeting of the Bank of Japan starts on Tuesday, they said. The yen moved just above 101 in morning trade before steadying.
It has been a choppy couple of weeks for major currency markets, hamstrung this year by a lack of clear differentiation between the economic stories of Japan, Europe and the United States.
Growth is now moving at different rates, although official borrowing costs in all three remain near rock bottom. Signs the European Central Bank is preparing to loosen monetary conditions even further knocked the euro back last week. The single currency gained about 0.2 percent on Monday just above $1.37 after a volatile session on Friday.
Merger activity around a handful of Britain's biggest companies has been one factor helping sterling this year, and some dealers said AstraZeneca's rejection of Pfizer's latest bid could put some pressure on the UK currency.
The pound's performance gave little sign of it by midday on Monday, however. Sterling, one of this year's better performers among the majors thanks to an improving economy, fell just 0.1 percent versus the euro and was almost unchanged against the dollar.
Investors also await minutes later this week of the Federal Reserve's April 29-30 policy meeting, as well as a private survey on China's manufacturing sector for May.
The dollar index stood just below 80, down slightly on the day after notching up a modest 0.2 percent gain last week.