The U.S. Democratic Party opened its national convention Monday to formally nominate Hillary Clinton as its candidate for the White House and rally public support for her bid to become the first female president in U.S. history.

The former secretary of state is scheduled to be officially anointed as the Democratic nominee on Tuesday and deliver an acceptance speech on Thursday, the final day of the four-day convention held at Wells Fargo Center in Philadelphia.

Clinton's vice presidential running mate, Virginia Sen. Tim Kaine, will also be officially nominated and make an acceptance speech on Wednesday.

Top Democratic leaders are slated to speak at the convention, including President Barack Obama, first lady Michelle Obama and Vice President Joe Biden, as well as Clinton's bitter primary rival, Vermont Sen. Bernie Sanders.

The party hopes to use the convention to strengthen unity after the toughly fought primary.

But such hopes were thrown into doubt following revelations from leaked emails suggesting that party officials unfairly favored Clinton over Sanders during the primary process. Debbie Wasserman Schultz, the chairwoman of the Democratic National Committee, offered to step down on the eve of the convention.

Sanders' speech, set for Monday, is expected to serve as a key barometer for unity.

Also Monday, the party adopted its policy platform which, among other things, pledges to strengthen the alliances with South Korea and other allies, and to work harder to make North Korea give up its nuclear and missile programs.

It also strongly lashed out at Republican presidential nominee Donald Trump for praising North Korean leader Kim Jong-un, encouraging the proliferation of nuclear weapons, and threatening to abandon treaty allies South Korea and Japan.

"North Korea is perhaps the most repressive regime on the planet, run by a sadistic dictator. It has conducted several nuclear tests and is attempting to develop the capability to put a nuclear warhead on a long-range missile that could directly threaten the United States," the document said.

"The regime is also responsible for grave human rights abuses against the North Korean people. Yet Donald Trump praises North Korea's dictator, threatens to abandon our treaty allies, Japan and South Korea, and encourages the proliferation of nuclear weapons in the region. This approach is incoherent and rather than solving a global crisis, would create a new one," it said.

The party will "protect America and our allies, press China to restrain North Korea, and sharpen the choices for Pyongyang to compel it to abandon its illegal nuclear and missile programs," the platform said.

On economic issues, the party was critical of free trade and vowed a review of trade deals.

"Over the past three decades, America has signed too many trade deals that have not lived up to the hype. Trade deals often boosted the profits of large corporations, while at the same time failing to protect workers' rights, labor standards, the environment and public health," the draft said.

"Democrats believe we should review agreements negotiated years ago to update them to reflect these principles. Any future trade agreements must make sure that our trading partners cannot undercut American workers by taking shortcuts on labor policy or the environment," it said. (Yonhap)