Haas Formula 1 boss Gunther Steiner believes Renault will "try anything instead of focusing on themselves to get better" as the two teams' fight for fourth place increases in intensity.
Renault has occupied best-of-the-rest spot in the constructors' championship for most of this season but has lost out in the development race and its performance has dropped.
Haas would be ahead of Renault had Romain Grosjean not been excluded from the Italian Grand Prix for an illegal floor, a matter that arose because Renault protested its rival.
Nico Hulkenberg said his Renault team will have a "long end to the year" on its current form and in Japan Haas cut the gap to just eight points - a tally it will regain if it wins its appeal against Grosjean's Monza exclusion.
Asked by Autosport if Haas smells blood as Renault's form has dropped, Steiner said: "I just see their performance has gone down, I don't know what's going on internally.
"For sure they dropped their performance, and their engine they make themselves so they can have nobody to blame.
"If they confuse themselves even more, it's better for us - I'm not against it!
"You could see that they were a little bit desperate when they put the protest in against us in Monza.
"They'll try anything instead of focusing on themselves to get better."
There are four races left for Haas to overhaul Renault and Steiner said he is in "no hurry" for his team to do the job.
"It's still difficult," he said. "I know we have four races to go.
"They were not very strong this weekend [at Suzuka] but they were luckier than us and scored a point but their performance and their pace was not good.
"But that doesn't mean that they're not going to be good in Austin and Mexico.
"We need to have our guard up and do a good job. We are not there yet.
"We will fight but there's still a long way to go, still four races, still 20% of the championship."
Steiner has previously stated he wants his team to win fourth place on-track and not rely on its appeal being successful.
That case will be heard at the start of November, after the United States and Mexican GPs are held back-to-back.
"We all go back to the UK straight after Mexico and then we have got three days to prepare ourselves and go in there," said Steiner.
"I fly back from Mexico straight to the UK with everybody else and we take it from there."