Chevron Corp. on Tuesday filed a countersuit against trial lawyers and their consultants for what it says was a campaign to rig the Ecuadorean court system in a bid to win billions of dollars in a pollution claim.

The step is the latest in an 18-year-old court battle that Chevron says is driven by U.S. trial lawyers looking for a big payday, not the 30,000 Ecuadoreans who are allegedly victims of environmental damage due to oil exploration and extraction.