The coronavirus pandemic is a blow to McLaren's steady rise up the grid, team boss Andreas Seidl has admitted.

After a slump spanning several years, McLaren had improved more recently and was looking forward to the opportunity of the new 2021 rules.

But not only have the rules been postponed until 2022, McLaren must now modify its current car for 2021 to accommodate the switch from Renault to Mercedes power.

Any modifications for actual performance, though, will not be allowed.

"The FIA will closely monitor in detail what the integration into the chassis will look like," Seidl told Auto Motor und Sport.

"It is clear that we really can only change what is absolutely necessary to integrate the Mercedes engine."

Seidl said it is a definite blow to McLaren's earlier hopes to step boldly towards the top three teams for 2021 and beyond.

"It was well known that we are a big fan of the new technical rules because they should help us on the way up the grid. But we absolutely supported the postponement due to cost reasons," he said.

"But by postponing the new rules, there will definitely be a delay for us now on our journey back to the top of the field."

Seidl said McLaren's plans for a new wind tunnel and simulator are also on hold for the pandemic.

"The shutdown at our company and also at Mercedes is currently pausing the whole project," he said.