Benitez is desperate to add more players to his squad before the transfer window closes on Wednesday night.
United’s manager had wanted the club to complete its transfer business by January 20 to give him more time to work with new arrivals.
However, Benitez – who has signed Kenedy on loan from Chelsea – doesn’t know if the Newcastle’s hierarchy will deliver him the players he thinks he needs to keep the club in the Premier League.
United’s 3-0 FA Cup defeat to Chelsea at Stamford Bridge yesterday highlighted the need for another striker.
Benitez, happy at the club and on Tyneside, is prepared to consider a new contract – if he and owner Mike Ashley are on the “same page” when it comes to transfers.
Asked about the situation, Benitez said: “I think our fans are very clever.
“They know what’s going on, and I want to make sure I don’t let them down, so I want to keep going, because I’m a professional and I want to do well.
“I’m happy in the city, with the fans and I can see the potential of the club, but we have to be sure that everyone has the same message, the same ideas, and that we are all on the same page.
“We have to keep working hard. I will keep working as hard. I’m working now with all my staff and all my players to improve the team.”
Benitez – who wants to sign Feyenoord striker Nicolai Jorgensen – says he has “confidence” that the club would strengthen before the deadline.
“Until the 31st, I have to give my confidence,” said Benitez, whose 15th-placed side take on Burnley in a Premier League fixture on Wednesday night.
Asked if he had spoken to managing director Lee Charnley at Stamford Bridge, Benitez added: “No, we didn’t have time. We were just concentrating on the game.”
Benitez was also asked in the Stamford Bridge press room how much longer he could continue with limited resources.
“I just have to be worried about Burnley – and that’s it,” said the 57-year-old.
Benitez has made midfielder Jack Colback available for transfer, while winger Rolando Aarons and defender Jamie Sterry could also leave on loan before the deadline.
Aleksandar Mitrovic could be sold to a club on the continent if United sign a striker, but Benitez says it would be “difficult” to sell fringe players Henri Saivet and Massadio Haidara.
Midfielder Saviet and defender Haidara were handed starts against the Premier League champions, who booked their place in the fifth round thanks to two goals from Michy Batshuayi and a strike from Marcus Alonso.
“It’s very difficult that they will leave,” said Benitez, who was angered by the club’s failure to strengthen his squad in the Championship a year ago.
Mitrovic – who is ready to quit the club this month – wasn’t involved against Chelsea.
The Serbia internaitonal wants to play regularly ahead of the summer’s World Cup finals in Russia.
Asked if the striker had played his last game for the club, Benitez said: “If he stays here, he can play. If he doesn’t stay, he will not play. But, at the moment, he’s our player.”
Benitez – who fielded Karl Darlow in goal at Stamford Bridge – also wants to sign an experienced goalkeeper this month.
Asked for an update, Benitez said: “I have no idea at the moment. We’re trying to do business. Still, we’ll see, as we have time. Hopefully, we can do something.”
Rob Elliot wasn’t involved in the fourth-round defeat because of what Benitez described as a “small” injury.