Sen. Elizabeth Warren will endorse Hillary Clinton 'soon': Reuters

Senator Elizabeth Warren will soon endorse presumptive Democratic presidential nominee Hillary Clinton and, while not currently interested in serving as her running mate, has not ruled it out, several sources close to Warren told Reuters.

Advisers to Warren, a fiery critic of Wall Street and a popular figure among progressive Democrats, have been in close contact with Clinton's campaign team and the conversations have increased in frequency in recent weeks, the sources said.

Warren, 66, represents her home state of Massachusetts in the U.S. Senate. The sources said that foremost in her thinking is how best to help the Democratic Party defeat the presumptive Republican nominee Donald Trump in the Nov. 8 presidential election and advance issues such as income inequality which top Warren's agenda.

An endorsement of Clinton could come within a week or two, one of the sources said. Clinton has been appealing for Democratic Party unity. On Twitter over the weekend, Warren echoed that call and emphasized the importance of the party coming together to beat Trump.

“Get ready, Donald,” she tweeted. “We're coming.”

Warren has stayed neutral in the Democratic primary race, notably remaining the only woman senator not throwing her support behind the first woman presidential nominee of a major political party.

Were she to join the Clinton ticket, she could help energize progressives and win over supporters of Clinton's rival Bernie Sanders, a democratic socialist U.S. senator from Vermont. Sanders' calls for reining in Wall Street and breaking up big banks dovetail with Warren's views.

Warren, a former special adviser in the Obama administration for the Consumer Financial Protection Bureau, has been one of the Democrats' most effective Trump critics.

An ongoing feud with Trump gained steam on social media with a series of posts in which she labeled the celebrity businessman racist, sexist and xenophobic and said she was going to fight to make sure his “toxic stew of hatred and insecurity never reaches the White House.”

Warren joined Clinton late last month in criticizing Trump for rooting for the 2008 financial crisis and delivered a 10-minute invective on the subject at an annual Washington gala two weeks ago.

“What kind of a man roots for people to get thrown out of their house? I’ll tell you exactly what kind of man does that,” Warren said. “It is a man who cares about no one but himself - a small insecure money-grubber who doesn’t care who gets hurt so long as he makes a profit off it.”

Trump has ridiculed Warren by calling her Pocahontas in a mocking reference to her having said in the past that she had Native American ancestry. Pocahontas was a famous Native American in early colonial Virginia.

(Additional reporting by Megan Cassella and Amanda Becker in Washington; Editing by Amran Abocar and Howard Goller)