Russian President Vladimir Putin on Wednesday congratulated Barack Obama with his victory in a tightly-fought U.S. presidential election vote that was greeted with relief in Moscow.

The Kremlin said Putin had reacted "positively" to Obama's victory over Mitt Romney after a campaign that saw the Republican Party challenger refer to Moscow as Washington's chief geopolitical foe.

The main opposition Syrian National Council voiced hope on Wednesday that resolving the conflict in Syria would figure at the top of re-elected U.S. President Barack Obama's agenda.

"We hope President Obama places Syria among the priorities in his foreign policy to put an end to the crisis and achieve the aspirations of the Syrian people to choose their own government and their own president, just like the American people did," leading SNC member Radwan Ziadeh told Agence France Presse.

Palestinian President Mahmoud Abbas on Wednesday congratulated U.S. President Barack Obama on his re-election and called on him to pursue Middle East peace efforts.

Abbas "congratulated U.S. President Barak Obama on his re-election as U.S. president for a second term," said a statement carried by official news agency WAFA.

Israel Prime Minister Benjamin Netanyahu on Wednesday congratulated U.S. President Barack Obama on his re-election, saying ties between their two countries were "stronger than ever."

"The prime minister congratulates the president of the United States for his victory in the election," Netanyahu said in a statement. "The strategic alliance between Israel and the United States is stronger than ever."

EU leaders on Wednesday congratulated Barack Obama for his reelection to the White House, saying they look forward to boosting ties with the United States and cooperating on global challenges.

European Union President Herman Van Rompuy, who was first to react, wrote on his Twitter account: "Very happy about the reelection of President Obama."

Republican challenger Mitt Romney conceded defeat in the U.S. election early Wednesday, telling supporters that he had called President Barack Obama to congratulate him on his victory.

"His supporters and his campaign also deserve congratulations," he said, in a brief address at his election watch party in Boston.

U.S. President Barack Obama said late Tuesday the American people have "picked ourselves up" and fought back during tough economic times, declaring after winning re-election that the "best is yet to come."

"In this election, you, the American people, reminded us that while our road has been hard, while our journey has been long, we have picked ourselves up, we have fought our way back," Obama said at a triumphant victory party in Chicago.

As Americans troop to the polls to decide between President Barack Obama and Republican challenger Mitt Romney, here's a guide to what to watch for on election night:

+ POLLS CLOSE: The continental United States covers four times zones from east to west. The first polling stations close at 7:00 pm Eastern Time (0000 GMT) in Georgia, Indiana, Kentucky, South Carolina, Vermont and Virginia. Polls close in California and several other western states at 11:00 pm Eastern Time (0400 GMT). Everyone will be watching for early results in the battleground state of Virginia as a potential bellwether of the night ahead.

President Barack Obama said he expects to have "a good night" by the end of election day Tuesday, and congratulated his Republican rival Mitt Romney for waging a "spirited campaign."

Obama spent the day in his hometown Chicago meeting with volunteers and calling some of them up personally to thank them for their work, before he hosts a results watch party in the city.

Republican presidential hopeful Mitt Romney cast his ballot Tuesday in the U.S. elections with his wife Ann before heading to Ohio and Pennsylvania for one last push to get out the vote.

The Romneys voted at the Beech Street Center in the town of Belmont, Massachusetts, the community center where they voted in the Republican primary in March.