FACTBOX: Key facts on Japan-China trade

(Reuters) - China's President Hu Jintao heads to Japan on Tuesday for the first visit by a Chinese president in a decade.

Trade between the two Asian giants has grown steadily, despite tense political relations. Following are some details about the economic relationship between the two.

* ECONOMY

Japan remains the biggest economic power in Asia, with a $4.3 trillion economy in 2006, against China's $2.7 trillion, according to World Bank data.

* TRADE NUMBERS

China replaced the U.S. as Japan's top trade partner in 2007, with two-way trade totaling $236.6 billion, the Japan External Trade Organization (JETRO) reported.

According to Chinese customs authority statistics, Japan was China's third biggest trade partner, behind the European Union and the United States, last year.

* IMPORT/EXPORT

China overtook the United States as Japan's biggest export destination in 2007, for the first time in modern history. Exports to China and Hong Kong combined stood at 17.4 trillion yen ($165.2 billion), compared to 16.9 trillion yen to the United States.

China's exports to Japan were worth $102 billion in 2007, an increase of 11.4 percent on the previous year.

* MUTUAL INVESTMENTS

Japan's foreign direct investment to China stood at $6.2 billion last year, down from its peak of $6.6 billion in 2005, according to JETRO.

Traffic in the other direction is a comparatively new area of growth. Chinese banks can invest their clients' money in Japanese stocks and mutual funds since February.

* CURRENCY SWAP

China and Japan have a $6 billion currency swap agreement, created to thwart speculative attacks on their currencies and prevent a repeat of the Asian financial crisis.

($1=105.32 Yen)

Sources: Reuters, Japan External Trade Organization

(Writing by Candida Ng, Singapore Editorial Reference Unit; Additional reporting by Chris Buckley in Beijing and Yoko Kubota in Tokyo)