(Recasts, adds Greenpeace comment)

MEXICO CITY, May 25 (Reuters) - Mexico promised to plant 250 million trees this year and get aging trucks and buses off the roads in a plan to fight global warming launched on Friday, but did not set clear greenhouse gas emissions targets.

President Felipe Calderon, handing out trees at a ceremony to promote his national climate change strategy, said there would be cleaner gasoline, more wind energy and more use of solar power in houses, especially in Mexico's sun-baked north.

"The fact that other big countries are not disposed to take on the responsibility and continue to damage the environment must not be an excuse to feign ignorance of our own responsibilities," Calderon said.

But environmental group Greenpeace criticized the strategy, saying it lacked firm targets to cut emissions of greenhouse gases.

"Unfortunately the plans are very ambiguous, there is no concrete methodology, no measurable goals. It is not enough," said Greenpeace spokeswoman Cecilia Navarro.

Mexico is one of the major developing countries that will take part in a global warming summit in Germany in June.

The United States has rejected Germany's bid to get the Group of Eight industrialized countries to agree at the meeting to tough cuts in carbon emissions which cause global warming.

Mexico, a major oil producer, uses mostly fossil fuels to generate electricity.

It has many environmental problems, including massive illegal logging and old buses and trucks that belch black smoke into the air and pollute cities.

The country's carbon emissions amount to about 4 tonnes per person each year. The United States produces closer to 20 tonnes per person.

The Mexican plan wants to take off the roads all buses and trucks that are at least 10 years old from next year and to plant 250 million trees in 2007.

Calderon, a former energy minister, also said he wanted to increase Mexico's wind power generation tenfold. Mexico has a naturally windy zone in the south where wind farms already exist.

The plan also envisions increasing independent power generation and co-generation alongside the state oil and gas monopoly Pemex.

Calderon said cleaning up public power companies and making them more efficient were an integral part of the plan. He said Pemex and electricity companies CFE and Luz y Fuerza should clean up their acts.

"Unfortunately I am fully conscious that perhaps our biggest challenge is in our own government-owned companies," Calderon said.

Global warming is blamed mainly on fossil fuels and deforestation. Rising world temperatures have brought more deadly hurricanes, droughts and floods, experts say.

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