"I've spoken with Armed Forces commander in chief, General Luis Trigo, who has precise instructions to safeguard and defend the Bolivian people," Morales told a meeting of pro-government labor unions in the central city of Cochabamba on Saturday.
"The government will protect the (oil) pipelines and (gas) valves," he added.
The move to put all government-owned energy installations under military guard followed protest plans to throw up major roadblocks in the energy-rich eastern provinces of Santa Cruz, Chuquisaca and Tarija starting Monday.
The demonstrators are against Morales's decision to tax regional revenues from gas fields. Provincial governors are demanding the government return 166 million dollars already raised through the levy, and substantially increase the price of gas exports to neighboring Argentina and Brazil.
Protesters are also venting anger at an upcoming referendum on constitutional reforms approved in December by Morales' followers in Congress that would expand the president's socialist agenda and his executive powers.
The opposition governors in charge of Santa Cruz, Beni, Pando, Tarija and Chuquisaca -- half the territory of South America's poorest nation -- are backing protests against Morales.
On Tuesday, during a 24-hour strike observed in five of Bolivia's nine states, clashes occurred between opposition youths and pro-Morales indigenous supporters. Five people were hurt in the stone-throwing melees.
Morales, Bolivia's first indigenous leader, won support of two-thirds of the country in an August 10 referendum for his policies, which include nationalization of key industries and changes to give more land and national revenues to the indigenous majority.
But the plebiscite also strengthened the mandates of the opposition governors.
The situation has deepened a political crisis in the country, and there are fears sporadic violence could broaden into open conflict.
Most of Bolivia's oil fields belong to state-run YPFB company, after the government in forced buyouts in May and June secured controlling shares in several foreign oil companies operating in the country.
Bolivia is South America's second-largest natural gas producer after Venezuela.