Voting has begun in the United States for the midterm elections, widely viewed as a test of President Donald Trump's performance during the first two years of his administration.

All 435 seats in the House of Representatives and 35 Senate seats are being contested.

Polling began first in Vermont at 5 a.m. local time. Voting stations in New Hampshire, New Jersey, New York and Virginia opened at 6 a.m. Alaska and Washington were scheduled to open their final polling stations at 11 a.m., while voting in Hawaii was due to begin at noon.

According to media reports, Democrats are in a strong position to gain control of the House of Representatives, while the Senate race remains uncertain. Democrats need three additional seats to secure a House majority and four seats to gain control of the Senate.

The reports identify the war with Iran, rising fuel prices and inflation as key factors affecting Trump's approval ratings. If Democrats take control of the House, they could gain greater authority to investigate the Trump administration and block some presidential nominations.