The Magpies have signed Ki Sung-yueng and Fabian Schar this summer but Benitez has been calling for more to be spent to keep up with their Premier League rivals.
There has been speculation lately of a swap deal involving West Brom striker Salomon Rondon and Dwight Gayle but the proposed switch appears to have stalled.
With the transfer window due to close on August 9, it gives the Tyneside club limited time to bolster their squad for the upcoming campaign.
Benitez watched his Newcastle side get thumped 4-0 by Portuguese club Braga in a friendly on Wednesday and revealed he is still in the dark over any potential arrivals.
“I said what I had to say on transfers two months ago, we’ll see what the next 10 days bring,” said the Toon boss.
“I have no idea – I have no idea how close we are to anyone.
“Now is not a time to talk about [Salomon] Rondon or Gayle, it’s a time to analyse what’s gone on these last two months.
“I said two months ago what we needed, and 10 days before the start of season we have four or five players we thought we could bring but we haven’t – and we still are where we are.”
Asked for his thoughts on Newcastle’s poor result Benitez admitted it is a concerning time for the club.
He added: “It was a bad game for us, we’re not doing well on the pitch or off it.
“It’s concerning with the season 10 days away. That should be a wake-up call for everyone (at the club). If we don’t improve everything we will suffer.
“The only positive was the attitude of the young players.”