The demonstration, organized by the Democratic Progressive Party, is the first large protest against Ma's policies since he took office last May promising to boost Taiwan's sluggish growth and ditch his predecessor's pro-independence, anti-Beijing line.

Opposition lawmaker Huang Wei-che said an estimated 300,000 people will attend the demonstration in the capital, Taipei, with many being bused in from the south, the DPP's stronghold.

Over the past year, the Harvard-educated Ma has helped to ease tensions with the communist-run mainland, which views Taiwan as a breakaway province. The two sides split amid civil war in 1949.

Ma has lifted long-standing bans on direct transportation links and relaxed control on Taiwanese investment on the mainland.

The opposition says Ma's overtures weaken Taiwan's sovereignty and might even force the island to accept eventual unification with the mainland — a charge that the president denies.

But Sunday's mass rally — ahead of Ma's first anniversary as president Wednesday — does not seem to have come at an opportune time for the DPP to make its cause known to the wider population.

Over the weekend, Taiwan's Health Minister Yeh Chin-chuan arrived in Geneva as head of an official delegation to attend the World Health Organization's annual assembly for the first time as an observer.

It is widely seen as a step that might help raise the international standing of the island.

Taiwan's participation at the WHO assembly was made possible after China dropped its long-standing objection, apparently in response to Ma's repeated appeals for Beijing to end its diplomatic blockade of the island.

But the DPP says Ma's policies have failed to ease soaring unemployment, which stands at a record high of 5.8 percent as the island's exports have fallen sharply amid the global economic recession.

Taiwan's growth contracted by a record 8.4 percent in the last quarter of 2008 and is expected to decline by at least a further 3 percent for all of 2009.