FRANKFURT (Reuters) - Deutsche Boerse's DB1Gn.DE supervisory board is reluctant to approve quickly an extension of Chief Executive Carsten Kengeter's contract following the German exchange operator's failed merger with the London Stock Exchange LSE.L, two people close to the matter said.

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Carsten Kengeter’s contract as Chief Executive is due to expire in March 2018.

German blue-chip firms usually renew board member contracts a year before they expire, but such a contract extension is not a priority for Deutsche Boerse’s directors, who are due to meet in late April, the sources said.

Deutsche Boerse declined to comment on Kengeter’s possible contract extension.

One of the main factors preventing Deutsche Boerse from giving Kengeter another full term is a pending investigation into insider trading, the sources said.

German financial watchdog Bafin handed over the findings of an investigation into allegations of insider dealing against Kengeter to public prosecutors in February.

Kengeter and Deutsche Boerse deny that a share purchase program, awarded shortly before Deutsche Boerse announced merger talks with the LSE, amounted to anything improper.

Some investors have already said that they would like Kengeter to be replaced if he is officially charged by public prosecutors.

A spokeswoman for the Frankfurt prosecutor’s office on Wednesday said it remained unclear how long the insider trading investigation would take to be concluded.

The merger, which was the exchanges’ fifth attempt to combine, would have created Europe’s biggest stock exchange, but was struck down by European regulators after LSE failed to comply with a small antitrust-related demand.

Kengeter has been criticized for underestimating the political dimension of the merger and failing to assure political backing in Germany.