DUBAI (Reuters) - Qatar's ruler has appointed a new prime minister, the office of Emir Sheikh Tamim bin Hamad Al Thani said on Tuesday, choosing a close associate for an influential role that seeks to ensure the emir's writ runs throughout the Gulf State's administration.

The change comes as Qatar gears up to host the 2022 World Cup, which it hopes will boost its economy and international influence, and coincides with surging U.S.-Iran tensions and a lingering quarrel between Qatar and some Gulf Arab neighbours.

Sheikh Khalid bin Khalifa bin Abdelaziz Al Thani will take on the role of prime minister after Sheikh Abdullah bin Nasser Al Thani, who was also Qatar's interior minister, submitted his resignation to the emir.

The new premier Sheikh Khalid, aged around 51, who will also take on the post of interior minister, had been the head of the Amiri Diwan, the emir's office.

Key cabinet positions such as foreign, energy, finance, defence and trade ministries remained unchanged.

Analysts said the change was not unexpected.

"This is a new generation taking the reins," said Majed al-Ansari, an analyst and professor of political sociology at Qatar University, referring to the relative youth of some of the officials working with Sheikh Tamim, who is in his late 30s.

Ansari added that the move does not seem to signal any major shift in Qatar's direction.

"The new prime minister is very close to his highness the emir, part of his inner circle," Ansari said.

Sheikh Abdullah, thought to be around 60 years old, on Twitter thanked the emir for his guidance during his time as prime minister.

The emir also appointed a new commander of the internal security forces, Abdulaziz bin Faisal bin Muhammad Al Thani, state news agency QNA said.

Saudi Arabia, the United Arab Emirates, Bahrain and Egypt cut diplomatic and trade links with Qatar in June 2017, accusing it of backing terrorism. Doha denies the charge and accuses its neighbours of seeking to curtail its sovereignty.