Bernie Sanders stand together during a campaign rally where Sanders endorsed Clinton in Portsmouth, New Hampshire.
Mrs Clinton, 68, hopes the joint appearance will help her win over Mr Sanders' supporters, some of whom carried his signs into the rally and frequently drowned out her backers.
"This campaign is not really about Hillary Clinton, or Donald Trump or Bernie Sanders, or any other candidate who sought the presidency".
"You should know that in the weeks since the last primary, both campaigns have worked together in good faith to bridge some of the policy issues that divided us during the election".
"Bernie Sanders, who has lost most of his leverage, has totally sold out to Crooked Hillary Clinton", Trump wrote on Twitter.
Democratic U.S. presidential candidate Hillary Clinton and Sen.
A day earlier in an interview to Vox, Clinton said she expressed concern over IT workers being displaced and being asked to train people.
The 74-year-old USA senator from Vermont vows to work hard to make the former Secretary of State become president. "And on our worst days, I think it is fair to say we are 100 times better than any Republican candidate", he said during a Democratic debate February 4, 2016.
Though Sanders said repeatedly that he would vote for Clinton in the general election after her edge on him grew so significant that she was deemed the presumptive Democratic presidential nominee, he has not yet endorsed.
Since becoming the presumptive nominee, Clinton has campaigned alongside President Obama and Massachusetts Sen. Elizabeth Warren, a liberal stalwart popular with Sanders' followers.
In a statement, the Trump campaign said Sanders was now officially part of the rigged system he had criticized during his long primary battle with Clinton. He warned that people will "see no increase in the minimum wage of $7.25 an hour", which he described as a "starvation wage" if Trump become the next President. Democrats head to their party convention in Philadelphia, where Clinton will be formally nominated later this month'.