By Ehab Farouk

CAIRO, May 15 (Reuters) - A senior Egyptian Finance Ministry adviser involved in talks on a vital IMF loan has resigned, suggesting that newly appointed bureaucrats loyal to President Mohamed Mursi's Muslim Brotherhood had meddled in his work.

Sami Khallaf's resignation, announced on Wednesday, points to friction resulting from Brotherhood-linked appointments in the civil service. The Islamist group's sway over Prime Minister Hisham's government was increased by a reshuffle last week.

Khallaf, who told Reuters he had resigned on Tuesday, was an adviser to the minister and head of the ministry's public debt unit. He had been involved in talks on a $4.8 billion loan Egypt is seeking from the International Monetary Fund.

"They try to disrupt my work and interfere in it as well as marginalise me ... There is no link between my ideas and theirs," Khallaf said, referring to the new appointees.

He said the work of the new group of officials who had entered the ministry had a "political nature".

Advisers from the Brotherhood's Freedom and Justice Party won posts in the ministry after cabinet changes in January and May. Finance Minister Fayyad Abdel Moneim, appointed in the latest reshuffle, is a professor specialised in Islamic economics, but not a Brotherhood member.

The opposition accuses the Islamist group of trying to take over the state in a process it dubs "Brotherhoodisation".

The Brotherhood says it has every right to make political appointments given that Mursi came to power via the ballot box, and denies accusations that it aims to dominate.

Another senior Egyptian Finance Ministry official, Hany Kadry Dimian, also a point man in IMF talks, resigned in late April but retracted the resignation several days later.

Negotiations with the IMF have stumbled repeatedly over government resistance to austerity measures that would include increasing sales tax and curbing subsidy spending - steps needed to get the deficit under control.

The new reshuffle has compounded criticism of the Mursi administration's management of an economy facing severe budget and currency crises that have been temporarily eased by $5 billion in financial assistance from Qatar and Libya.

A senior U.S. diplomat said: "Some of the recent cabinet appointments have been disappointing, and particularly in the economic sphere."

Angus Blair, founder of the Cairo-based think tank Signet Institute, said: "The market is not yet convinced of the ability of the cabinet to come up to solutions to Egypt's problems." (Additional reporting by Tom Perry; Writing by Asma Alsharif; Editing by Patrick Werr and Tom Perry)