LA PAZ, Bolivia – President Morales ordered soldiers to immediately occupy Bolivia’s natural gas fields yesterday and threatened to evict foreign companies unless they sign new contracts within six months giving Bolivia majority control over the chain of production.

Mr. Morales said soldiers and engineers with Bolivia’s state-owned oil company would be sent to installations operated by foreign petroleum companies.

“The time has come, the awaited day, a historic day in which Bolivia retakes absolute control of our natural resources,” Mr. Morales said in a speech from the San Alberto petroleum field in southern Bolivia to decree a nationalization of the natural gas industry. The field has been operated by Brazil’s Petroleo Brasileiro SA in association with the Spanish-Argentine Repsol YPF SA and France’s Total SA.

Bolivia has South America’s second largest natural gas reserves after Venezuela, and all foreign companies must turn over most production control to Bolivia’s cash-strapped state-owned oil company, Yacimientos Petroliferos Fiscales Bolivianos, Mr. Morales said.

An Army spokesman did not immediately return a telephone message seeking comment on when and how the military would act.

Mr. Morales had pledged to exert greater state control over the industry since he won the presidency in December in a landslide.

Multinational companies that produced 100 million cubic feet of natural gas daily last year in Bolivia will be able to retain only 18% of their production, with the rest being given to YPFB, he said. Mr. Morales did not name the companies.

Other major petroleum companies doing business in Bolivia, besides Petroleo Brasileiro and Repsol, include Britain’s BG Group and BP and American-based Exxon Mobil Corporation.