By Patricia Zengerle

WASHINGTON (Reuters) - A senior U.S. senator said on Tuesday he would like to pass legislation to extend expiring sanctions on Iran and enable Congress to quickly enact new ones if necessary over the country's ballistic missile tests.

The Iran Sanctions Act, which imposed nuclear, missile and terrorism sanctions on Iran, expires at the end of 2016, and both Democrats and Republicans in Congress support extending it.

But Senator Ben Cardin, the top Democrat on the Senate Foreign Relations Committee, acknowledged that lawmakers have not yet unified behind a proposal that would attract enough votes to pass and become law.

"Members have different views," he said at a roundtable discussion with reporters.

The Obama administration has warned Congress that it would oppose new sanctions that interfere with the international nuclear pact, laying the groundwork for a potential fight over any legislation.

Senator Bob Corker, the committee's Republican chairman, has said he is working on legislation with Cardin that he hopes will attract strong bipartisan support. That measure has not yet been unveiled and aides said they had no more information about when it might be introduced.

Cardin was one of several Democrats who joined every Republican in Congress in opposing the nuclear agreement with Iran announced last July. But he has urged lawmakers to accept it since a Republican-led effort to block the pact failed in September.

After the deal went ahead, Cardin filed legislation meant to increase U.S. oversight of it. That bill never came up for a vote in the Republican-controlled Senate.

Cardin said he still felt that bill was valid and wants to amend it to extend the Iran Sanctions Act and create a "legislative framework" so sanctions could be imposed quickly if Iran pursues its ballistic missile program.

Late last month, two Democratic senators who supported the Iran nuclear agreement, Tim Kaine and Chris Murphy, introduced a separate bill to extend the Iran Sanctions Act until Obama can guarantee Iran's nuclear program is purely peaceful.

And Republican Senator Kelly Ayotte, with 18 other senators form her party, introduced a separate bill that would extend the Iran Sanctions Act through 2031 and require new sanctions over Iran's ballistic missile efforts.

Senator Mitch McConnell, the Senate Majority Leader, has said he wants any Iran bill to come to the floor with at least the 67 votes needed to override a presidential veto.

(Reporting by Patricia Zengerle; Editing by David Gregorio)