WASHINGTON - U.S. President Barack Obama on Tuesday welcomed Afghanistan President Hamid Karzai's acceptance of a run-off election on November 7, saying it was an important step forward for democracy.

It is now vital that all elements of Afghan society continue to come together to advance democracy, peace and justice. We look forward to a second round of voting, and the completion of the process to choose the president of Afghanistan, Obama said in a statement.

The heavily disputed August 20 vote had complicated Obama's decision on whether to send thousands more U.S. troops to Afghanistan to fight a resurgent Taliban.

U.S. officials have suggested that Obama may not wait for the outcome of the run-off election before deciding whether to approve a request by his top military commander in Afghanistan, General Stanley McChrystal, for 40,000 or more reinforcements.

Obama praised Karzai's constructive actions saying they established an important precedent for Afghanistan's new democracy.

Relations between Karzai and the Obama administration have been at a low point since the disputed election. Karzai was angered by Washington's refusal to recognize him as the winner of the poll.

The Afghan constitution and laws are strengthened by President Karzai's decision, which is in the best interests of the Afghan people, Obama said in the statement.

(Reporting by Ross Colvin, editing by Matt Spetalnick and Jackie Frank)