Jose Maria Lopez says his World Endurance Championship Toyota LMP1 drive takes precedence over a place in Formula E, as drivers affected by the two series' clashes outlined their positions.
The announcement of the ABB FIA FE calendar last week revealed three clashes with the WEC, and FE has said it it will not rearrange its calendar to alleviate the problem after FIA president Jean Todt said the FIA would look for a solution to the clashes.
Ferrari's Sam Bird, Toyota pair Lopez and Sebastien Buemi, Rebellion's Andre Lotterer and Aston Martin's Alex Lynn could potentially continue into the next WEC season.
Lopez has yet to begin talks with Dragon but is keen to remain in FE, and admitted prioritising Toyota could make it a difficult task.
"My priority is Toyota, as a programme," Lopez told Autosport.
"I have a contract with Toyota for next year and all the races. My intention is to [also] continue in Formula E."
Lopez's Toyota team-mate Buemi - who stayed at the e.dams-run team when Nissan took over the operation from Renault in 2017, despite its rivalry with Toyota - admitted his situation was more "complex".
"It's complex [to prioritise a drive] because it depends on the race," Buemi told Autosport.
"For some of the races, Formula E is the priority and for some of the others, WEC is the priority."
Buemi suggested there could be some flexibility due to the fact that a two-driver crew is possible in the four and six-hour races.
Two-driver crews would be possible at an eight-hour event but would be unlikely due to concerns over driver fatigue, and Toyota has Thomas Laurent as a reserve driver option in 2019/20.
Buemi added: "Of course, Le Mans, for example, I have priority with WEC. Not all [of the WEC season], because some races in the WEC need three drivers and some need only two.
"What is a shame is that there is a [calendar] committee and nobody is trying to find a solution [to the clashes], I still hope they will find a solution.
"I'm not too worried right now."
Envision Virgin Racing's Sam Bird has been a factory Ferrari driver in the WEC since 2016, but he has confirmed his FE commitments will take priority - though says he is "disappointed" by the clashes.
Lotterer and Lynn both suggested their situation was different from the likes of Buemi and Lopez because of their differing contract status.
DS Techeetah's Lotterer drove for the LMP1 privateer Rebellion squad during the WEC's 2018/19 campaign, but he has suggested he would not continue into next season.
He told Autosport: "This [the clashes] is quite a problem for some drivers. For me, not so much.
"I was going to focus on Formula E most likely anyway. I don't have a works seat in WEC, so it's not such a big problem as it is for Seb, for example."
Lynn stepped in for Nelson Piquet Jr at Jaguar mid-season and the Aston WEC driver does not have a contract with the FE team beyond the end of 2018/19.
Lynn told Autosport: "I'm in a different situation because I'm firmly in WEC and filling in at Formula E. That's [my future] a conversation that will happen later on when it becomes relevant."
Jaguar team boss James Barclay said in the pre-Swiss E-Prix press conference that a decision on Lynn's future would be made in "due course" and praised his driver's performances to date.
Alberto Longo, Formula E's deputy CEO, was asked by Autosport for his view on drivers' being compromised by the calendar.
"Well at some point they need to make a decision," he said.
"I know Formula E is big enough today in order for them to make a decision to be in one championship or the other.
"If they want to share both championships, which is completely respectful and I kind of like it, they need to decide [what to do] if there is a clash.
"It's not even their decision I can imagine, it's their teams' decisions in both championships and their contracts with both teams will be deciding which championship they're going to race that weekend."