Provisional figures reported on Japanese Finance Ministry's web site showed January imports rose 7.3 percent year-on-year to 6.428 trillion yen, while exports rose 6.4 percent to 4.799 trillion yen, leaving a deficit of 1.63 trillion yen. In the same month of last year, the deficit was 1.48 trillion yen ($15.83 billion).
Japan is the world's third-largest economy after the United States and China. The new government led by Prime Minister Shinzo Abe has been trying to lift the country out of its chronic deflation and boost exports through a number of stimulus measures.
These measures have helped bring down the value of the yen against the U.S. dollar, which should help boost exports as was evident in the January figures. But a weaker yen, which has fallen more than 12 percent since January of last year, also makes imports more expensive.
January imports rose for the third straight month as oil product imports jumped 33.7 percent and liquefied natural gas rose 11.4 percent, Kyodo News reported, quoting the Finance Ministry.
Japan ended 2012 with a record trade deficit of 6.93 trillion yen, or $78 billion.
Part of the reason for Japan's rising trade deficit is its growing territorial dispute with China over the Senkaku Islands in the East China Sea, which both claim. The dispute has led to violent protests in China, hurting Japanese exports and adversely affecting bilateral trade, which before the dispute averaged more than $340 billion annually.