NEW YORK -  US president-elect Donald Trump officially nominated ExxonMobil Chief Executive Officer Rex Tillerson for secretary of state on Tuesday, setting up a possible confirmation battle over the nominee's oil business ties to Russia.

While Democrats and even some Republicans raised questions about Tillerson's relationship with Russia — accused of interference in the recent presidential election — Trump praised his fellow businessman as "a world class player" who has led one of the world's largest corporations.

"His tenacity, broad experience and deep understanding of geopolitics make him an excellent choice for secretary of state," Trump said in his statement.

In his new role at the State Department, Trump said Tillerson would "promote regional stability and focus on the core national security interests of the United States. Rex knows how to manage a global enterprise, which is crucial to running a successful State Department, and his relationships with leaders all over the world are second to none."

In a statement, Tillerson said he shares Trump's "vision for restoring the credibility of the United States’ foreign relations and advancing our country’s national security."

The nominee pledged to "focus on strengthening our alliances, pursuing shared national interests and enhancing the strength, security and sovereignty of the United States.”

The Senate must still confirm Tillerson, and some members of the Republican majority have raised the Russia question.

"I expect the US-Russian relationship to be front and centre in his confirmation process," Senator Lindsey Graham, a Republican, said.

Tillerson's ExxonMobil duties involved working on major oil projects with Russia, including a partnership with the Russian oil giant Rosneft.

In 2013, Russian President Vladimir Putin awarded Tillerson the Order of Friendship, one of the highest honours the nation bestows on foreign citizens.

Republican Senator Marco Rubio — one of Trump's rivals in the Republican primaries, and a lawmaker who tweeted he did not want a "friend of Vladimir" at the State Department — said he has "serious concerns" about Tillerson's nomination.

"The next secretary of state," Rubio said, "must be someone who views the world with moral clarity, is free of potential conflicts of interest, has a clear sense of America's interests, and will be a forceful advocate for America's foreign policy goals."

Senator John McCain, a senior Republican leader, told CBS News that Tillerson's ties to Russia may well be "strictly commercial," and that's "fine," but the issue will be aired in confirmation hearings.

"Certainly it should be a matter of concern," McCain told CBS' news programme Face The Nation. "But I am sure, in a bipartisan way, he will get a fair hearing."