Van Hollen would not say what changes he expects to be made. But any tinkering by the Senate will require House approval and could delay the measure's enactment.
The House approved the original measure by a 219-206 vote, with 36 Democrats opposing it largely because it exempted the National Rifle Association from complying with its requirements.
House passage of the bill was anything but smooth. Its original vote was pulled from the schedule as Democratic leaders tried to appease concerns their members had with the bill.
A diverse set of organizations, ranging from the U.S. Chamber of Commerce to the American Civil Liberties Union, also opposed the legislation and ran an aggressive campaign to defeat it by claiming it trampled on First Amendment rights.
Proponents of the bill hope it becomes law before campaigning for the November election heats up.
However, a Senate vote on the measure remains unclear. Senate Majority Leader Harry Reid (D-Nev.) joined other Democratic leaders from his chamber and vowed that a vote would occur on the bill. But Reid has yet to say when the measure will come to the floor.