Former US secretary of state Hillary Clinton is heavily favored to beat leading Republican candidate Donald Trump in the presidential election in November if they end up facing each other, Chinese observers said.

In the latest Super Tuesday primaries in northeastern states, Trump easily defeated rivals John Kasich and Ted Cruz in all five states - Pennsylvania, Maryland, Connecticut, Rhode Island and Delaware, with a margin of victory rivaling that of his home state of New York a week ago. Clinton defeated Senator Bernie Sanders in four states, only losing to him in Rhode Island, Reuters reported.

According to the Associated Press, Clinton, who has amassed 2,141 delegates, needs 2,383 to win, while Trump is 287 short of 1,237 delegates needed to lock up the nomination. Cruz and Kasich have 560 and 153 delegates, respectively.

"Clinton has the advantage of super delegates, which will make it very difficult for Sanders to catch her. On the Republican side, Kasich and Cruz are unlikely to triumph over Trump in delegate numbers, and there's a strong possibility Trump will win the remaining primary contests," Sun Chenghao, an assistant research fellow at the Chinese Institutes of Contemporary International Relations, told the Global Times.

At a speech before the polls closed, Cruz said his campaign was now heading to "more favorable terrain." The Cruz and Kasich campaigns on Sunday announced a team up in the Indiana primary on May 3, Oregon's May 17 primary and New Mexico's June 7 contest.

Sun said he doubts team-up tactics can help the two candidates due to bad timing and a possible public backlash. "Even if Trump fails to secure the 1,237 delegates needed before the convention, he is likely to fill the gap and secure the nomination during the first round at the convention," he said, referring to a contested convention in July in Ohio.

Exuding confidence, Trump said it was time for Cruz and Kasich to get out of the race so the party can unify behind him. "I consider myself the presumptive nominee," he said.

Clinton's advisers and allies have begun discussions on a possible running mate, The New York Times reported.

However, many Republicans oppose Trump and may vote for Clinton instead during the general election. Meanwhile, many social elites who have not participated in the primaries will vote in the general election, which may also lead to more changes, Sun noted. "Electing a president is different from the primaries. This is also why Trump adopt a more serious tone in the campaign."

Trump is scheduled to deliver a foreign policy speech in Washington on Wednesday local time. The speech will address several critical foreign policy issues, including global trade and building up the US military.