US Secretary of State Rex Tillerson delivers remarks to Department of State employees upon arrival at the Department of State in Washington, US, February 2, 2017. [Photo/Agencies]

Within hours of starting the job, Tillerson reached out by phone to counterparts from Mexico and Canada, spoke by phone with Israeli Prime Minister Benjamin Netanyahu and met with German Foreign Minister Sigmar Gabriel, department officials said.

Hundreds of State Department officials greeted the former Exxon Mobil Corp chief executive with applause as he entered the building. Louder cheers broke out when Tillerson thanked acting Secretary of State Tom Shannon for standing in after the departure of John Kerry.

"Hi, I'm the new guy," said Tillerson, who was sworn in on Wednesday after the Senate confirmed him to his post despite concerns about his ties with Russia. Trump has called for closer relations with Russian President Vladimir Putin.

In remarks that did not touch on foreign policy specifics, Tillerson addressed the dissent within the department that emerged this week in a memo signed by more than 900 officials in protest against Trump's decision to suspend the US refugee program and restrict travelers from seven Muslim-majority countries.

"One of the great challenges and thrills for the State Department staff is deciding how to confront changing conditions in every corner of the world," said Tillerson, "I encourage all of you to use your natural and well-developed skills to adapt to changes here at home as well.

"I know this was a hotly contested election and we do not all feel the same way about the outcome," said Tillerson.

"Each of us is entitled to expression of our political beliefs, but we cannot let our personal convictions overwhelm our ability to work as one team," he added.

He also signaled he would impose changes to improve the functioning of the department and said the security of diplomats was a priority.