US presidential candidate Bernie Sanders has begun shifting the Democratic Party toward rebuking Israeli crimes against the Palestinians, putting pressure on his rival Hillary Clinton to handle a growing divide within the party.

Support for Israel has long been a policy of the Democratic Party, but consensus on the issue has eroded in recent years.

Tensions between the administration of President Barack Obama and Israel have increased and so has the strain among liberal Democrats about Israel's policies toward the Palestinian people.

Last year, Obama and many fellow Democrats were angered when Republican lawmakers scheduled an address to Congress by Israeli Prime Minister Benjamin Netanyahu in which he condemned Washington’s nuclear deal with Iran.

The scale of civilian casualties in Israel's attack on the Gaza Strip in 2014 also alienated many liberal Democrats. Nearly 2,200 Palestinians, including 577 children, were killed in Israel’s onslaught. Over 11,100 others - including 3,374 children, 2,088 women and 410 elderly people - were also injured.

Democratic presidential candidate Hillary Clinton speaks at an event on May 25, 2016 in Buena Park, California. (AFP photo)

Despite those tensions, Clinton and many party leaders are still eager to show their unwavering support for Israel, largely due to the deep political support Israel enjoys among top officials in both political parties.

In contrast, Sanders, who is Jewish and has spent months of his youth living in Israel, has spoken of seeking a more “evenhanded” treatment of Palestinians.

In an interview with The Los Angeles Times on Wednesday, Sanders declared himself “100% supportive of Israel’s right to exist.” Israel, he said, has a right “to take all actions that are needed to protect itself from terrorism.”

“But I believe that for too long our country and our government have not given the Palestinian people the respect that they need,” he added. “Long term, if there’s going to be peace in the Middle East, a lasting peace, the Palestinian people are going to have to be treated with respect and dignity."

According to polls, a majority of Americans support Israel, but the Democratic Party is increasingly split over some of the actions of Israel and how much sympathy to express for the plight of Palestinians.

However, among liberal Democrats surveyed in a poll taken last month, 40 percent said they sympathized more with Palestinians than Israel, compared with 33 percent who sympathized more with Israel.

Sanders supporters also expressed more sympathy with the Palestinians than with Israel, the poll found. His campaign has paid attention to concerns from many liberals, including Jewish liberals, that the suffering of Palestinians has been ignored in mainstream US politics and that criticism of the Israel is less tolerated here than it is even within Israel.