TOKYO (AFP) - Japan posted its third straight current account deficit in January, as trade losses swelled on the weakening yen and strong energy imports, the government said on Friday.

The shortfall in the current account, the broadest measure of Japan's trade with the rest of the world, came to 364.8 billion yen (S$4.7 billion) in the month, down 19.9 per cent from a year earlier, the finance ministry said.

But the deficit was much smaller than a 626-billion-yen gap expected by economists polled by Dow Jones Newswires and the Nikkei.

The current account measures not only international trade in goods but also services, tourism and Japan's foreign investments abroad.

The latest figures were mainly due to a massive 1.48-trillion-yen trade deficit in the month, the ministry said.

"The trade deficit expanded for five months in a row as imports of mineral fuels increased," offsetting growing exports to the United States and Asia, the ministry said in a statement.

The figures underlined Japan's continued struggle in international trade, where its exports have been lacklustre and its energy imports elevated due to stalled domestic nuclear plants, analysts said.

"The recent weakness of the yen also contributed to the deficit," Mr Hideki Matsumura, an economist at the Japan Research Institute. "Japan is likely to continue suffering trade and current account deficits for the time being."