The admission comes as the software giant is widely expected to miss its target of 2.75 to three million consoles shipped in the 90 days since launch on 22 November.
Analysts estimate that 1.3 million consoles were shipped by the end of last year but warned that sales since the new year have been limited by shortages.
Microsoft announced at the Consumer Electronics Show in Las Vegas that 4.5 to 5.5 million units would be shipped by 1 July this year.
Microsoft also admitted to production glitches. "This is a complex piece of hardware with 1,700 different parts," said a spokesman.
"Every now and again the line will slow down because something has happened and there will be a component that did not make it that morning."
Why does Facebook store "my entire call history with my partner's mum", asks developer who requested his Facebook data
Facebook database included text-message metadata - despite not using Facebook Messenger for SMS
Before Ocado could start selling the technology it had developed to other retailers, it had to tear down and rebuild its own monolithic architecture
Successful attack could result in harm to patients and financial loss, warns NHS governing body
Guccifer 2.0 claimed to be a lone Romanian hacker - until a schoolboy error gave him, her or them away