Whoever, being an officer, clerk, agent, employee, or other person charged with the payment of any appropriation made by Congress, pays to any clerk or other employee of the United States, or of any department or agency thereof, a sum less than that provided by law, and requires such employee to receipt or give a voucher for an amount greater than that actually paid to and received by him, is guilty of embezzlement, and shall be fined under this title or in double the amount so withheld, whichever is greater, or imprisoned not more than two years, or both; but if the amount embezzled is $1,000 or less, he shall be fined under this title or imprisoned not more than one year, or both.