The 20 January swearing-in ceremony is expected to draw record crowds
Online auction site eBay has banned the resale of tickets for the inauguration of Barack Obama as US president.
Some 240,000 tickets for the ceremony are to be handed out to the public for free by members of Congress.
But with record crowds likely to flock to Washington for the 20 January event, there are fears those with tickets may seek to make money by selling them on.
StubHub, another popular online ticket site, has also prohibited the resale of the inauguration ceremony tickets.
Democratic Senator Dianne Feinstein, who chairs the Joint Congressional Committee on Inaugural Ceremonies, said she was crafting a bill that would make it a federal crime to sell tickets to the historic event.
"These tickets are given for free to people," Ms Feinstein said.
"This is a major civic event of the time, and no-one pays for their tickets, and we believe no-one should be required to pay for their tickets."
Ms Feinstein said she foresaw overwhelming demand for the 240,000 available tickets and had heard reports they might sell for as much as $40,000 online.
She said her own Senate office had received 8,000 ticket requests on the first day after the election.
Other measures are being put into place to prevent "scalping". Congressional offices will not receive the tickets until shortly before the inauguration and people will be required to pick them up in person.
The National Park Service has said it is planning for crowds of at least a million people for the inauguration ceremony.
Giant screens will be sited along the National Mall leading up to the steps of the Capitol, where the swearing-in will take place, to allow people to watch.