United chief executive David Gill has indicated funds are available to his manager to spend this summer, but Ferguson says he is happy with the balance of his squad despite their failure in the Premier League and Champions League last season.
The United manager has already signed rising Mexican star Javier Hernandez from Guadalajara and defender Chris Smalling from Fulham, and a raft of new faces had been expected to follow.
But Ferguson will place his trust his existing squad and his latest crop of youth and reserve players if he is unable to pinpoint any new signings.
Speaking alongside Gill at a press conference in New York to promote United's four-game North American tour this summer, Ferguson said: "In the market today it's very, very difficult and the structure of our squad is good in terms of ages, the balance, the numbers and there's a lot of good young players.
"Sometimes you have to trust in all the development of the last few years and I'm going to stick with that, or most of it.
"There may be one signing and maybe we'd like to get a good player to the club, of course, but it's not easy in the present day climate and I've nothing definite to tell you because we're still assessing whoever's available and the difficulties in terms of who you'd bring in."
Gill added: "Hernandez and Smalling are signings we've already made and the other point to bear in mind is that the Premier League is bringing in squad limits next year of 25, which we clearly operate [in European competitions] but is now coming to the Premier League.
"There will be unlimited under-21s and other rules and we'll be taking all that into consideration."
To that end, Ferguson also revealed he would not be replacing goalkeeper Ben Foster with a new signing, instead promoting England Under-21 international Ben Amos to the first-team squad alongside Edwin Van der Sar and Tomasz Kuszczak.
Foster is close to completing a £6million move to Birmingham and the United manager is confident 20-year-old Amos has a bright future at Old Trafford.
"When we decided to let Ben (Foster) go, we were in the process of letting a good young goalkeeper, Ben Amos, go out on loan," Ferguson said.
"He's in the England Under-21 team but we can only accommodate three goalkeepers. So when the situation with Ben's future at Manchester United came into it and we agreed to let him go, we stopped Ben Amos from going on loan.
"He will now be our third goalkeeper, he's very talented and has a good future ahead of him."
All three keepers are likely to travel across the Atlantic with the United squad this summer.
The club will have a training camp in Chicago followed by friendlies against Celtic in Toronto on July 16, the Philadelphia Union in Philadelphia on July 21, the Kansas City Wizards in Kansas four days later, and the MLS All-Stars in Houston on July 28.
Ferguson will give his World Cup players leave of absence from the tour, which will move on to Mexico and a game against Guadalajara, which was agreed as part of the deal to sign 21-year-old forward Hernandez.
Depending on Mexico's progress in South Africa, Hernandez is pencilled in to feature in the game.
Ferguson added: "It depends when his last game is for Mexico.
"Normally we give the players 28 days' rest but in the case of Hernandez we'll bring him to Philadelphia as soon as his games with Mexico are finished.
"The simple reason is he's young and I think he can handle coming in for training but, more importantly, it's for him to integrate into the squad because he doesn't know any of the players."