"We do still expect you to testify before Congress," she said in a tweet, while congratulating Page on "the move".

She added that while Google co-founder Page's title may have changed, he is still a part of Alphabet's board of directors and retains "effective control".

Sundar Pichai, who has been the chief executive officer of Alphabet's Google for four years now, succeeded Page at the helm of Alphabet on Tuesday, making him the public face of a company long associated with its iconic founders.

Warren, vying for the Democratic nomination to take on President Donald Trump in November 2020, has vowed to break up Amazon.com Inc, Google and Facebook Inc if elected to promote competition in the technology sector.

(Reporting by Neha Malara in Bengaluru; Editing by Shailesh Kuber)