Red Bull Racing management is to meet with Renault after the Monaco Grand Prix to discuss their future together.
The French manufacturer currently supplies the team with power units badged under the TAG Heuer brand. Their association goes back to 2007 and includes four world championship seasons.
However relations have become strained in recent seasons. Red Bull has been increasingly unhappy at their engine's performance and reliability compared with those of Mercedes and Ferrari.
The current agreement between the companies comes to and end after 2018. At present, Red Bull has no alternative engine supplier signed up, although junior team Toro Rosso is working with Honda for the first time this season.
Decision time is fast approaching, with Renault insisting that an agreement must be agreed this month if they are to continue supplying engines for another season.
"We cannot postpone it indefinitely," Renault boss Cyril Abiteboul told El Mundo newspaper this week. "We are not going to put a deadline, because it's not our style.
"But there is some urgency due to changes in the regulations. So if Red Bull wants our engines, they should let us know."
The manufacturer had previously said May 15 was the latest date for an agreement for Red Bull to be assured an engine next year under Formula 1's current rules. It later extended that cut-off date to May 31.
Now, Abiteboul's latest comments suggest that there won't even be a meeting between the two parties until May 28 at the earliest. That's the day after the Monaco Grand Prix.
He has said that while it would prefer to continue its association with Red Bull, it would also be prepared to walk away.
"If there is no agreement, we will stay with Renault and McLaren," Abiteboul said. "We do not have to supply three teams."
One person with a particular interest in developments between Renault and Red Bull is driver Carlos Sainz. The former Toro Rosso driver came into the support through the Red Bull junior driver development programme.
Sainz is currently on a one-year loan to the Renault works team as part of a complicated deal by which McLaren moved to Renault engines, and Toro Rosso to Honda power units.
"We all know about his Red Bull contract," Abiteboul said, agreeing that he would like to see Sainz remain at Enstone long-term beyond the end of 2018. "We are also all aware that, if there is a will by all parties, there is a way to end it.
"I am convinced that there will be many occasions to talk about this matter soon," he added. "We have been talking with Red Bull about all kinds of issues for 12 years."