TOKYO, Jan 17 (Reuters) - Japanese government bonds took a breather on Thursday as a few investors took profits after the benchmark yield touched a four-week low, but expectations of Bank of Japan easing steps next week supported the market. * The BOJ will mull taking additional stimulus action and doubling its inflation target to 2 percent at its Jan. 21-22 meeting, sources close to the central bank have said. * "Ahead of the BOJ meeting, some people see no reason to sell bonds, but after this week's gains, short-term traders are booking profits," said a fixed-income fund manager at a Japanese asset management firm in Tokyo. * The 10-year JGB yield was flat at 0.745 percent, after slipping to an intraday low of 0.740 percent, its lowest since Dec. 18. * The 10-year JGB futures contract ended morning trading down 0.05 point at 144.26, on track for its first losing day after a four-session rising streak. Futures rose as high as 144.37 on Thursday, their highest since Dec. 14. * The superlong sector was also steady, with the yield on the 20-year bond flat at 1.730 percent and the 30-year bond yield flat at 1.960 percent. * On Wednesday, the BOJ bought 22.7 billion yen ($257 million) worth of exchange-traded funds to prop up the equities market, a common step when the broader Topix loses more than 1 percent in the morning session. Japanese shares were moderately higher on Thursday.