Pedro de la Rosa admits he is "not confident" that HRT will make the 107 per cent qualifying margin at the United States Grand Prix.
De la Rosa and team-mate Narain Karthikeyan as well as test driver Ma Qing Hua were well off the pace of Sebastian Vettel during both practice sessions at the new track in Austin on Friday. The Spaniard's best time of 1:44.453 in the afternoon was 6.735s slower than that of the Red Bull driver.
HRT, who have qualified for every single race since missing the season-opening Australian GP, know they need to find a bit of extra pace on Saturday if they are going to make it to the grid for Sunday.
"I'm not confident," de la Rosa told Autosport. "It is marginal.
"It will depend on whether we manage to get into the tyre-temperature window, which we were definitely not getting on Friday. This is our biggest issue.
"We are slower than at other tracks mainly because we are not working the tyres at all, not the prime nor the option. They are just like new after a 10-lap run.
"The track evolution was so low because there is no tyre wear, therefore the asphalt doesn't pick up rubber.
"That makes me think that Saturday is going to be difficult for us. If the track evolution proves to be similar to Friday, then we will have problems and it's going to be a tough qually for us."
The 41-year-old completed only 29 laps on Friday and there were suggestions that it was related to some financial problems, but De la Rosa was quick to dismiss the claims.
"We had the tyre issue and we thought it was quite useless to run first thing in the sessions when the track was slippery," he said.
"If we had tyres that switched on initially, then we should have run more."