TOKYO Jan 23 (Reuters) - Japanese government bonds mostly slipped on Wednesday, giving back some of the gains made in the previous session when the Bank of Japan doubled its inflation target to 2 percent and committed to open-ended asset purchases.
* Japan's central bank pledged to extend asset buying into 2014, with no time-limit and an initial plan to buy 13 trillion yen in mostly short-term bills in that year.
* Some investors were disappointed that the open-ended buying would not begin until 2014, but the scope of the measures was greater than many had expected. JGBs were underpinned by expectations that the BOJ will have to take more easing steps and buy more assets to try to achieve its inflation target.
* "There was feeling that the BOJ isn't going to do much in the near-term, but overall, their commitment to easing is supportive for JGBs, particularly short- and medium-term maturities," said a fixed-income fund manager at a Japanese trust bank in Tokyo.
* The 10-year JGB yield added 1 basis point to 0.740 percent, while benchmark 10-year JGB futures slipped 0.13 point to 144.32 in morning trade.
* The 30-year bond was the session's only gainer so far, its yield creeping down half a basis point to 1.965 percent.
Superlong maturities came under pressure in the previous session on fears that the aggressive monetary policy will trigger inflation in the long term, and also on supply concerns ahead of a 20-year sale on Thursday.
The 20-year yield rose half a point to 1.745 percent.
* The five-year yield added 1 basis point to 0.155 after drooping as low as 0.140 percent on Tuesday, the lowest recorded since Japan started issuing 5-year bonds in 2000.