Russian President Vladimir Putin Wednesday, November 9 congratulated Donald Trump on his victory in U.S. elections, hoping to work with him to improve relations, the Kremlin said in a statement, AFP reports.

As the nail-biting election extended into early Wednesday, the rest of the world was contemplating the reality of President Trump in the White House.

Before Hillary Clinton conceded the race, a senior member of German Chancellor Angela Merkel's government said the geopolitical situation was "very uncertain."

meanwhile, leaders of the European Union institutions invited Trump to a summit as soon as he can schedule one and cited security and trade ties as key in a letter on Wednesday, Reuters says.

"Today, it is more important than ever to strengthen transatlantic relations," wrote Donald Tusk and Jean-Claude Juncker, presidents respectively of the European Council, which groups member states, and the executive European Commission.

Also, NATO chief Jens Stoltenberg congratulated him and said U.S. leadership was "as important as ever" at times of new security challenges from hybrid warfare to cyber attacks to terrorism.

"A strong NATO is good for the United States, and good for Europe," Stoltenberg said, stressing that the trans-Atlantic alliance must remain strong.