Apple Chief Executive Tim Cook has written an editorial in the Wall Street Journal urging US senators to support the Employment Non-Discrimination Act (ENDA).
The Senate is expected to take a vote today on whether to enshrine the bill into US law.
The act would protect workers against discrimination based on sexual orientation and gender identity.
Mr Cook is widely considered to be one of the most influential gay businessmen in the world, although he has never spoken publicly about his sexuality.
When he was appointed as Apple’s CEO in August 2011, Tim Cook was dubbed the “most powerful gay in Silicon Valley”.
He wrote in the Wall Street Journal: ”Long before I started work as the CEO of Apple, I became aware of a fundamental truth: People are much more willing to give of themselves when they feel that their selves are being fully recognised and embraced.”
Mr Cook added: “Those who have suffered discrimination have paid the greatest price for this lack of legal protection. But ultimately we all pay a price. If our co-workers cannot be themselves in the workplace, they certainly cannot be their best selves.
“When that happens, we undermine people’s potential and deny ourselves and our society the full benefits of those individuals’ talents.
“So long as the law remains silent on the workplace rights of gay and lesbian Americans, we as a nation are effectively consenting to discrimination against them.”
Yesterday, President Obama called on Congress to pass ENDA.
“Millions of LGBT Americans go to work every day fearing that, without any warning, they could lose their jobs – not because of anything they’ve done, but simply because of who they are,” he wrote in the Huffington Post.
“It’s offensive. It’s wrong. And it needs to stop, because in the United States of America, who you are and who you love should never be a fireable offense.”
It would be the first measure of its kind to advance to the floor in either house of Congress.
Previous versions of the bill that have come to a vote have not included provisions for transgender people.