People in the United States are voting in a presidential election that is expected to be an extremely tight race.

Polling stations open at different times across the country. In the southern state of Virginia and some other states, on Tuesday, the polls started at 6 a.m.

US Vice President Kamala Harris and Republican nominee for president Donald Trump pitched for votes hours before the beginning of election-day voting in the presidential race.

On Monday, both Harris and Trump visited Pennsylvania, which has the most electoral votes among seven key battleground states.

Harris, a Democrat, spoke in the state's largest city, Philadelphia. She said, "It is time for a new generation of leadership in America, and I am ready to offer that leadership as the next President of the United States of America."

Seeking support, she added: "This could be one of the closest races in history. Every single vote matters."

Trump took part in a rally in Pennsylvania, too and then traveled to the state of Michigan where he delivered a speech after midnight.

The former president said that over the past four years, Americans have suffered one "catastrophic failure" after another.

He claimed that under Harris, living prices have soared and there is "economic anguish at home, war and chaos abroad."

"We're going to end that," he said.

Counting of votes cast Tuesday will start when the first polls begin closing in the evening.