The UK government gave the green light to build the 500MW station at South Hook in October.
But the joint owners announced on Monday that the proposal will now be deferred, due to falling prices in the energy market.
Building the plant would have involved several hundred workers, creating 30 permanent posts when completed.
The South Hook combined heat and power plant would have been sited at the LNG (liquefied natural gas) terminal and was due to be operational by 2018.
The project was a partnership involving Qatar Petroleum, Exxon Mobil and Elf Petroleum UK, who said their decision to put the plans on hold had been "difficult".
It is the latest blow to the area's energy ambitions, following the collapse of a deal to sell the neighbouring Murco oil refinery in November, with more than 300 job losses.
Plans to build a power station at a Milford Haven gas storage plant are being mothballed by owners.