The Thai army has made explicit its determination to use live ammunition against “red-shirt” anti-government protesters in certain circumstances.
An army spokesman told a regular news briefing that troops were ready to use their weapons “decisively”.
The red-shirts later called off plans to march on the city’s Silom business district, saying they wanted to avoid confrontation with the army.
Troops moved into Silom on Monday, in an increasingly militarised standoff.
The BBC’s Rachel Harvey says the army believes that some more militant members of the protest movement were preparing weapons such as sharpened bamboo sticks, acid and grenades.
“We can no longer use the soft to hard steps,” spokesman Col Sansern Kaewkamnerd told reporters.
“We have to keep a distance between troops and demonstrators. If they try to break the line, we will start using tear gas, and if they do break the line, we need to use weapons to deal with them decisively.”