Japan posted a record first-half trade deficit of $37.3 billion Wednesday as energy costs soared and exports to key markets slumped, while analysts warned of further pain for the next six months.

As the country struggles to recover from last year's quake-tsunami and nuclear crisis, costs have shot up while income has plummeted owing to the rolling debt crisis in Europe and a stuttering recovery in the United States and a strong yen.

The 2.9 trillion yen deficit stemmed largely from energy costs, with the resource-poor nation seeing a nearly 50 percent jump in purchases of liquefied natural gas and a 16 percent increase in crude oil shipments, the data showed.

Japan has struggled to meet its energy needs and has turned to pricey fossil fuel alternatives after its nuclear reactors were switched off following the crisis at the Fukushima Daiichi plant caused by the March 11 quake-tsunami.

"Japan's trade balance continues to show a trend of weak exports and extreme sensitivity to import prices, such as those of crude oil," said RBS Securities chief Japan economist Junko Nishioka.

"The crisis in Europe is posing a growing risk to Japan's economic recovery scenario."

In the first half, Japan's imports rose 7.4 percent on-year, while exports grew just 1.5 percent.

The country's trade surplus with the European Union during the first half was at a record low, according to the ministry, as vehicles and semiconductor shipments dived.

Europe is a major market for a wide range of Japanese products and Tokyo has repeatedly warned that the continent's economic woes would directly impact its recovery prospects.

May saw a bigger-than-expected trade deficit of about 907 billion yen, Japan's first monthly trade deficit with the European Union since records began in 1979.

Adding to the downward pressure on exports is the strengthening yen -- which is at a 12-year high against the euro -- as investors flock to the safe haven unit owing to uncertainty over the global outlook. Last year it touched a record high against the dollar.

The rise has prompted Tokyo to repeat warnings that the currency was overvalued, with officials in recent days hinting that they may intervene again in foreign exchange markets.

In afternoon Asian trade on Wednesday, the yen was at 94.39 against the euro and 78.18 on the dollar.

"While exports to Europe and China were already weak, we now see that export (growth) to the US may also be declining," Hideki Matsumura, economist at Japan Research Institute, told Dow Jones Newswires.

"I believe Japan will post another annual trade deficit. We're already in the red looking at the last six months, and it's too late to regain our losses."

Data for June alone, however, saw Japan post a better-than-expected trade surplus of 61.7 billion yen, instead of the market forecast for a 135 billion yen deficit, the official data showed.

But while it was the first surplus in four months, with the exports of vehicles and auto parts rising, some analysts said even those figures were less than encouraging for the world's third-largest economy.

"The trade deficit in the first half came from a larger scale of imports, but in June we are seeing something more fundamentally worrying," said Taro Saito, a senior economist at NLI Research Institute.

"Exports are weakening, in particular with the United States," he told AFP. "The trade surplus is only temporary. The economy will start logging a deficit from next month."

In June, exports to the United States, namely cars and auto parts, rose 15 percent from a year ago, well down from previous months.

"The US was the only driver for growth in the global economy, but it is now losing steam," Saito said.