(Corrects first paragraph to show a group of unions, not just the largest union, controls a block of seats in parliament)

By Aziz El Yaakoubi

CASABLANCA, Morocco, Feb 24 (Reuters) - Morocco's main trade unions, whose members control a sixth of the seats in parliament's upper house, held a one-day strike on Wednesday, before saying they would seek to block a government draft bill to reform pensions.

Public and private sector workers in Morocco's four largest labour unions went on strike for 24 hours in protest at government efforts to overhaul spending on pensions and subsidies.

Morocco has ended fuel subsidies and frozen public-sector hiring, winning praise from international lenders who say it has made better progress in controlling public spending than some other countries in the region.

Last month the government adopted a bill to reform the pension system.

But protests such as Wednesday's general strike, called by the Moroccan Labour Union (UMT) and three other union movements, have started to weigh on the Islamist-led government's plans to curb deficits and revive public finances.

"We have been facing a stubborn government which does not believe in dialogue, but ... in destroying people's purchasing power," UMT leader Miloudi Moukharik told Reuters, forecasting parliament would reject the pension bill.

"We have already delayed it three times inside the parliament and I can tell you that it will not pass."

Dozens of workers gathered in the headquarters of UMT and CDT, chanting slogans against government and foreign lenders such as the World Bank and the International Monetary Fund.

The strike disrupted the port of Casablanca, Morocco's biggest city, as well as transport and other sectors, a Reuters witness said. However, small shops, bars and cafes and some taxi drivers were working.

"We have always been in talks with the union and we will keep talking on the pension reform," Communication Minister and government spokesman Mustapha Khalfi told Reuters.

He said called the strike unjustified and said without reform, the pensions of 400,000 workers would be at risk because the government would not be able to finance them.

The pension bill reached the second house of Morocco's parliament last month but the government has so far failed to get it discussed.

Unions control 20 of the 120 seats in the upper house and experts say other opposition parties would join them in rejecting the reform.

Moukharik declined to give details on the unions' next move, saying they will meet to decide on action.

The proposed changes to state pension funds include raising the retirement age to 63 by 2019, and raising contributions, according to a government statement.

Workers will have to pay 14 percent of their salaries by 2019 and government contributions will rise in tandem, from 10 percent before the reform, adding 1 percentage point each year to meet the new plan.

(Reporting by Aziz El Yaakoubi; Editing by Patrick Markey/Ruth Pitchford) ((aziz.elyaakoubi@thomsonreuters.com; +212623934595)(;))

Keywords: MOROCCO STRIKE/