Vice President Joe Biden made a surprise visit to Washington, D.C.’s Naval Observatory on Saturday for a confidential talk with Sen. Elizabeth Warren (D-Mass.), CNN reported.

Biden’s return to the District comes amid buzz he is seriously weighing a 2016 Oval Office bid.

CNN said that two sources confirmed the pair’s face-to-face, the biggest indicator yet that Biden is seriously tempted by an Oval Office bid next year.

“The vice president traveled last minute to Washington, D.C. for a private meeting and will be returning to Delaware,” an aide told CNN. Biden spokeswoman Kendra Barkoff declined further comment on the alleged rendezvous.

CNN initially reported Saturday that Biden arrived in Washington around 11 a.m. and had planned on returning home to Wilmington, Del., later in the weekend.

Warren, a beloved figure in progressive circles, has resisted calls to mount her own presidential candidacy. She reportedly told WBZ radio in Boston on Friday that she considers the 2016 Democratic primary up for grabs.

“I don’t think anyone has been anointed,” said Warren, who has not yet endorsed a candidate.

Hillary Clinton, the heavy favorite for the party’s nomination, is currently grappling with sinking poll numbers amid voter concerns that she is neither a transparent nor trustworthy candidate.

Biden, 72, began mulling a third White House run following the death of his son Beau Biden in late May after a battle with brain cancer.

The vice president is widely expected to make a final decision next month. His entrance into the 2016 campaign would expand the Democratic field to six contenders.

Multiple national polls show Biden would have significant support from Democratic voters should he pursue the presidency next election cycle.

He previously ran for president in 1988 and 2004, both times dropping out early in the Democratic primary process.

biden and warren