By Joyce Liu

TAIPEI, Jan 15 (Reuter) - China's imperial treasures, open only to the country's royal family for thousands of years, travelled to Taiwan in 1949 with refugees who fled after the communist victory over the Nationalists in a civil war.

Chang Pi-teh still remembers the dangerous wartime journey from China nearly half a century ago. People piled on the decks of ships for the 220-km (137-mile) trip across Taiwan Strait impeded loading of the treasures. "That was an amazing scene," Chang said.

"When the last ship arrived in (Taiwan's northern) Keelung harbour, I asked myself, is this a refugee boat?" recalled the 74-year-old Chang, now deputy director of Taiwan's National Palace Museum, located at the foot of a mountain in a Taipei suburb.

Because the treasures confer a symbolic legitimacy on the regime which holds them, they were at the top of a list of items to be moved out of China when the Nationalist government retreated to the island after losing a civil war to the Chinese communists in 1949.

It was not the first wartime move for the treasures.

In the 1930s, they were transported to Zhongqing in China's southwestern Sichuan province from Beijing -- by train, truck and ship -- for safety reasons when China fought against the invasion by Japanese troops during World War Two.

Amazingly, 10 drum-shaped stone blocks, each weighing one tonne, from China's Warring States Period (475-221 B.C.) emerged unscathed from the journey to Zhongqing and back to Beijing, Chang said.

"Nobody could believe that the damage was so small when the boxes were opened," he said.

Soon afterwards, the treasures were moved south again because of the 1949 civil war, and then to Taiwan, where it took 23 months to complete cataloguing them.

Now, 47 years later, some of the treasures will be on the move again, this time to the United States, a country which Taiwan views as a priority in foreign relations.

Starting on March 12 this year, more than 400 masterpieces of painting, calligraphy and antiquities will tour four museums in the United States for 13 months.

Negotiations on the U.S. exhibition started in 1991 and it is still being hotly debated here whether some of the treasures should go abroad -- partly because they are fragile and, most important, because of fears that China may claim ownership when they are in the United States.

"We have to make sure nothing will go wrong. Any damage will be unforgivable in history," said Chang, who has spent more than 50 years with the treasures.

Taiwan and the United States reached agreement in December 1994 on the exhibition, dubbed the "Splendours of Imperial China."

"We have obtained the U.S. judiciary guarantee that all of them will come back to Taiwan after the exhibition," Chang said.

The collection, worth an estimated US$1 billion, will be put on display at the Metropolitan Museum of Art in New York City, the Art Institute of Chicago, the Asian Art Museum in San Francisco and the National Gallery of Art in the U.S. capital Washington.

Diplomacy is one of the reasons Taiwan agreed to lend the treasures. "The exhibition will enable the Republic of China (Taiwan) to use culture to expand the room for foreign relations," a museum statement said.

Only 31 countries recognise Taiwan, seen by China as a renegade province after the civil war ended in 1949. Washington switched diplomatic ties to Beijing from Taipei in 1979.

"We want to make the Palace Museum a world museum, and its works appreciated not only by the royal families in the past or by the Taiwan people now ," Chang said.

Before the end of China's Ching Dynasty (1644-1911), the treasures were open only to the royal family.

Taiwan is willing to share the treasures with other countries but not with their original home, although Beijing has said it would not confiscate the treasures if they were exhibited in China.

"We have a lot of concerns such as the security, the exhibition condition and the facilities. It is very unlikely we will display them in mainland China," Chang said.