SPRINGFIELD ‒ Despite pressure to weigh-in on the 2016 Democratic presidential race between Hillary Clinton and Bernie Sanders, U.S. Sen. Elizabeth Warren, D-Mass., refused to say Monday whom she will support and when that endorsement could come.

The senator, following am open house in Springfield, told reporters she hasn't decided when she'll announce what candidate she'll be supporting for president, but made clear "it's not today."

"No endorsements now," she said, adding that she's proud of her party's candidates for focusing on issues.

"I think that what the Democrats are doing is terrific. We're out talking about the issues," Warren said. "I look at the Republican debates and the difference between what they're doing and what the Democrats are doing that really shows who's on whose side."

The senator, however, hinted that her endorsement could come soon, saying "we'll see," when asked if she'll announce her support following the Iowa Caucuses.

The lone female Democratic U.S. senator to not come out in support of party front-runner Clinton, Warren has been credited with impacting much of the policy conversation on the Democratic side of the race, as both Sanders and the former secretary of state compete for her backing.

Warren has previously been critical of Clinton's relationship with Wall Street, telling Bill Moyers in a 2004 interview that as first lady she helped fight against bankruptcy legislation before reversing course and supporting it as a U.S. senator for New York.

When asked whether she still worries about Clinton's ties to the financial industry, Warren simply contended that she has "concerns about everybody's relationships with Wall Street."

"This is a rigged game and it's rigged because Wall Street makes sure that in every decision that gets made they're there," she told reporters. "They make sure they've got their lobbyists and their lawyers so that everything tilts just a little bit more their direction. This is what I'm fighting everyday in the United States Senate." Warren would not comment on whether she plans to back Sanders, with whom she shares several of the same political views and base of supporters.

Among those supporters is Amy Bookbinder, 68, of Northampton, who held a sign calling on the Massachusetts Democrat to endorse the Vermont senator's White House bid at the open house event.

"I think that she's been working right alongside him trying to save our democracy, trying to keep Wall Street from influencing in not so good ways and I think that she needs to endorse him and I hope she will," she told reporters.

Bookbinder said she "absolutely" believes Sanders and Warren are more aligned on the issues than the senator is with Clinton, adding that such an endorsement "makes sense."