Washington, June 11 (IANS): US Senator Bernie Sanders' refusal to quit the race even after Hillary Clinton won the Democratic nomination could hurt her efforts to unify the party to win the presidential election, experts said.

Clinton earlier this week finally grabbed the number of delegates needed to officially win. Still, Sanders on Thursday vowed to continue to compete and announced that he would run in the Washington DC primary next week, reports Xinhua news agency.

At a White House meeting with President Barack Obama, Sanders did not agree to drop out of the race.

He told the media he could continue in his fight against the wealth gap, in which upper income individuals and corporations continue to increase their wealth while the middle class and others struggle to make ends meet.

The firebrand senator from the state of Vermont said he wanted to prevent the country from becoming an oligarchy run by a few billionaires.

"Sanders wants to maintain his leverage over the platform, vice presidential selection, and future campaign rules," Darrell West, vice president and director of governance studies of the Brookings Institution, told Xinhua.

"He wants Democrats to take income inequality more seriously," West said.

Indeed, Sanders has run mainly on a platform that highlights the growing income inequality in the US where upper income people seem to be increasing their wealth while many middle-class people struggle to make ends meet.

"He feels that they provided an unfair advantage for Hillary Clinton and he wants to make sure that is not the case in 2020," West said.

While Clinton is a fellow Democrat, analysts noted that she represents everything that Sanders despises, as Clinton is a political insider whose celebrity has through the years allowed her to increase her personal wealth to the tune of millions of dollars.

Julian Zelizer, professor of history and public affairs at Princeton University, said that Sanders' campaign "had a message, it was a movement to tackle problems which in his mind neither party wants to address.

"By staying in the race he maintains the capacity to keep the media and the party focused on these questions," Zelizer told Xinhua.

Still, there is a point at which Sanders will have to exit or he will risk giving an advantage to Republican Party presumptive presidential nominee Donald Trump, Zelizer said.

West added: "Many Sanders voters will support Clinton because they understand the threat posed by Donald Trump. But it is crucial that she brings the party together as soon as possible so that she can focus full time on her Republican opponen."