Answer should be yes.
BUT, some companies have weird policies.
Go with whatever policy your company uses.

How can you assign a part number internally, if you don't know what it is? Generally, in the design phase, an internal part number may or may not be assigned until the product goes to production. This is usually accompanied by a list of acceptable parts (listing mfg and part number). Listing more than one mfg is usually a good idea to have an alternate source. Also, being the designer, you know what is important in the part your selecting so listing alternates is a good idea to prevent unacceptable parts being used later by another engineer less intimate with the project.

When assigning part numbers for a project it is convient if all part numbers for a project are in a block. (Less effort in finding parts later on)
So why not save a block of part numbers for a project?
So maybe parts 199321 through 199600 are requested with no manufacture or manufacture's part number.
Also some companies have just plain weird policies. I know, have worked for some of them.

The bottomline is that you should adhere to your company's policies, otherwise, you're in violation of ISO900x.

Internal part numbers can be given prior to any detailed design work or part identification.  In some cases, you know need a box that has certain functionality and you can assign a part number based on that functional partition.  Once you're in detailed design, all your part number should be based on actual parts or make/buy of some functionality.

TTFN