Last week, we reported that Nikon had filed a patent infringement suit against ASML. This week, we can confirm that ASML has filed a countersuit involving semiconductor manufacturing equipment, flat panel display manufacturing equipment, and digital cameras.

ASML dominates the market for lithography machines used by the world’s biggest chipmakers to make circuits ever smaller, faster, and more powerful. It generates around 80 percent of revenues in that market, ahead of No.2 player Nikon and No.3 Canon Inc, according to ratings agency Fitch.

The round of lawsuits and countersuits follows efforts to renegotiate a patent deal between ASML and Nikon that expired in 2014 and threatens to revive patent battles that stretch back to the turn of the century. ASML, Nikon, and Zeiss settled litigation in 2004 after the International Trade Commission found ASML had not infringed Nikon patents.

ASML denies infringing any of Nikon’s patents and claims it was left with no choice but to file counter-suits: additional suits will be brought in the United States, ASML said.

“Now that Nikon has decided to take this dispute to court, we also have to enforce our patent portfolio, and we will do this as broadly as possible,” ASML Chief Executive Peter Wennink said in a statement, adding it had tried for years to reach a cross-licensing agreement with Nikon.

Nikon said it had not yet received the complaints, according to Reuters.

“ASML and Zeiss’s retaliatory lawsuits are a predictable litigation tactic,” Nikon said in a statement, adding its own lawsuits targeted products that account for 76.3 percent of ASML sales last year, worth about 3.5 billion euros.