One of the two major umbrella unions in South Korea will launch a general strike on Wednesday to block the government's move to expand a flexible work hour system. 

In a news conference in front of the presidential office on Tuesday, the Korean Confederation of Trade Unions(KCTU) said that the government is moving to revise the labor law to expand the system. The umbrella union criticized the government for its "bad" labor policies and little progress in efforts to turn temporary workers into regular workers. 

The KCTU plans to hold a massive rally at 3 p.m. Wednesday in front of the National Assembly in Seoul. It expects about 150-thousand workers will participate in the strike nationwide. 

Under the current flexible work hour system, employers can add or reduce working hours for a three-month period in one year. The government is seeking to extend the period to as long as six months but workers are denouncing the move as an anti-labor policy.