Hillary Clinton, in bid for party unity, holds meeting with Elizabeth Warren

PresumptiveDemocratic presidentialcandidate Hillary Clinton met on Friday with U.S. SenatorElizabeth Warren, a leading progressive voice, to try to buildparty unity heading into her election campaign againstRepublican Donald Trump.

The two held talks at Clinton's Washington home a day afterWarren endorsed Clinton's White House bid, adding support fromthe Democrats' liberal wing as Clinton seeks to move on from herprotracted primary battle with Bernie Sanders.

Former secretary of state Clinton earlier this week securedthe delegates needed to win the party nomination for the Nov. 8presidential election. Party leaders are hoping Sanders willsoon drop his presidential run.

• Clinton leads Trump in the count that matters most
• Why Clinton needs no-surrender Sanders to make a graceful exit on his own terms

The Warren meeting on Friday fuelled speculation that thesenator from Massachusetts might be under consideration asClinton's running mate. Asked in an MSNBC interview on Thursdaywhether she had discussed with Clinton the prospect of beingvice president, Warren said she had not, nor had she beenvetted.

Having support from Warren would boost Clinton's ability tocourt highly motivated Sanders supporters who have been fired upagainst Clinton during the unexpectedly long primary battle.Warren and Sanders share views on issues such as reining in WallStreet excesses and fighting income inequality.

Sanders stays in

Sanders said on Thursday he would remain in the race throughthe final nominating contest in Washington, D.C., next week butwould work with Clinton to defeat Trump.

Warren is also shaping up to be a no-holds-barred critic ofTrump and they have had several spats on Twitter. Trump said onFriday that Warren was one of the "least productive U.S.Senators," adding in a tweet: "Hope she is V.P. choice."

President Barack Obama and Vice President Joe Biden alsoannounced their support of Clinton on Thursday, handing her atrio of endorsements expected to boost her standing heading intothe general election campaign.

But Clinton is dogged by the controversy surrounding her useof a private email server while secretary of state from2009-13.

Emails between U.S. diplomats in Islamabad and StateDepartment officials in Washington about whether to challengespecific drone strikes in Pakistan are at the centreof acriminal probe involving her handling of classified information,the Wall Street Journal reported on Thursday.

Republicans have consistently criticized Clinton over heremail use. "We should not live above the law, and that is one ofthe cardinal sins that Secretary Clinton violated," House ofRepresentatives Speaker Paul Ryan told radio host Hugh Hewitt onFriday.

Clinton has said she did not send or receive any informationthat was marked as classified and has accused the StateDepartment and other government agencies of "over-classifying"her emails after a judge ordered them released to the public.

• U.S. Senator Elizabeth Warren endorses Hillary Clinton