I have a prospective employer lined up for a job but they want me to work in the USA office, they've asked me to apply speculatively for an H1-B visa before they make a formal job offer.

If I proceed with the application with this employer, does it mean I cannot apply for other H1-B visas sponsored by other companies?

If possible, I would appreciate if you would please provide links to official sources in your responses to this question. Many thanks in advance for any information provided.