Over the years, relations across the Taiwan Straits have been frosty at best, and at worst have threatened to boil over into all-out war. Ever since the October Revolution in 1949, the communist government on the mainland has regarded Taiwan as a renegade province.

Beijing insists that Taiwan cannot be allowed to declare full independence and says it will use force if necessary to prevent it from doing so.

After the return of Hong Kong and Macau to mainland control, it sees the island as the last piece of the jigsaw needed to bring about the long-cherished dream of a reunited greater China.

For its part, Taiwan says the mainland government must acknowledge the de facto reality of Taiwanese nationhood before serious talks can begin.

As far as Beijing is concerned that is not an option.

When in 1999 Taiwanese President Lee Teng-hui suggested dialogue should be conducted along the lines of state-to-state relations, China responded with yet more sabre rattling and threats of invasion. Mr Lee, the Chinese media said, was "playing with fire".

With Taiwan now in the throes of its second democratic presidential elections, scheduled for 18 March, China is keen to show candidates and voters that it has the ultimate say over Taiwan's future.

'Red threat'

In the aftermath of the communist takeover, Chiang's regime held its position as the internationally-recognised government of all China and retained China's seat at the UN.

At a time of domino theories and fears of an expanding "red menace", Washington saw Taiwan as an "unsinkable aircraft carrier" that needed to be defended.

But by the late 1960s, the changing power politics of the Cold War and the Sino-Soviet split meant the US came to see Mao's People's Republic as a useful ally in its efforts to isolate the Soviet Union.

Secret negotiations led to President Richard Nixon's historic visit to Beijing in 1972 - paving the way for Beijing's accession to the UN, and ultimately for full diplomatic relations between China and the US.

'One China'

In line with Beijing's insistence on their being just "One China", Washington ended its diplomatic ties with Taiwan in 1979 in return for vague guarantees over its security.

Talks on possible reunification eventually began in 1993, but they were broken off by China two years later, angry at Taiwan's apparent attempts to forge an independent international profile.

A private visit by President Lee to the US in 1995 and the island's first democratic presidential elections the following year sparked a series of sabre-rattling Chinese military exercises close to Taiwan.

'Internal affairs'

Washington became so alarmed that it sent two aircraft carrier battle groups to the region - its largest show of force there since the Vietnam War.

Such statements further infuriated Beijing, not least because it regards Taiwan as an internal problem in which foreign governments have no place interfering.

Beijing wants Taiwan to accept reunification on much the same terms as Hong Kong and Macau - the so-called "one country, two systems" formula.

However, Taiwan says it will only consider unification if the mainland becomes more democratic.

Dire Straits

As China has slowly opened up to the outside world a steady rise in economic, cultural, family and business links with Taiwan have produced a steady impetus towards establishing closer formal ties.

Taiwan maintains a ban on direct investment in the mainland, but this has not stopped billions of dollars of Taiwanese money flowing into China via Hong Kong middlemen.

Slowly, both sides have shown a willingness to talk on practical issues that drive them together, particularly on economic and trade links.

But decades of separation have generated an increasingly wide gulf between Taiwan and the mainland.

It will take strong leadership on both sides to bridge the troubled waters of the Taiwan Straits.