UNITED NATIONS,(Reuters) – The United States urged U.N. Secretary-General Kofi Annan on Friday to persuade German prosecutor Detlev Mehlis to continue leading the probe into the killing of a former Lebanese prime minister into next year.

Mehlis, who began his investigation in May, has said he was only on the job for six months and would leave by the end of the year as head of a U.N. team looking into the assassination of Rafik Hariri and 22 others in Beirut in February.

The investigation was scheduled to end Dec. 15 but the U.N. Security Council will probably extend it after Lebanon asked that the commission, which has not finished its work, stay in business for another six months.

U.S. Ambassador John Bolton told reporters, &#34we understand he (Mehlis) has extended his tenure once and he”s in dangerous personal circumstances there,&#34 he said in reference to threats made against the prosecutor.

But Bolton said the United States had asked Annan to keep Mehlis in his post. If he does not agree, the United Nations should quickly name a successor. The best person for the job, Bolton quipped, would be &#34a clone of Mehlis.&#34

In a letter to Annan on Thursday, Bolton said the United States wanted Mehlis to &#34continue in his current capacity.&#34

&#34I am concerned that a wholesale change in the leadership of the commission would be exploited by the Syrian government to forestall their full and complete cooperation,&#34 he wrote.

In an October report, Mehlis implicated senior Syrian officials and their Lebanese allies, including President Bashar Assad”s younger brother, Maher, and his brother-in-law, Brig.Gen. Asef Shawkat, Syria”s chief of military intelligence. Syria has denied the accusations and called the Mehlis report politically motivated.

Mehlis has shown no sign of staying on the job, although U.N. spokesman Stephane Dujarric said he hoped the anti-terrorism prosecutor would help train a successor and remain &#34associated&#34 with the commission.

British Ambassador Emyr Jones Parry told reporters Mehlis” leave from his job in Berlin was limited.

&#34As I understand it, there may be a wish on the part of his bosses in Germany to get him back because he is very good police officer,&#34 Jones Parry said.

&#34If this (commission) is going to be renewed, we would much prefer commissioner Mehlis do it himself.&#34

Annan appointed Mehlis in May to lead what was expected to be a three-month criminal investigation. But the inquiry was extended once and Mehlis told Annan he could not stay more than six months.

His team will be in Vienna on Monday to interview five Syrian officials, including Lt. Gen. Rustom Ghazali, the former head of Syrian military intelligence in Lebanon.

Mehlis will be in New York the week of Dec. 12 to submit a new report and brief the Security Council, Jones Parry said. Britain is president of the Security Council in December as well as head of the European Union and the Group of Eight industrial nations.

The council has warned Syria to cooperate with the investigation or face the prospect of further action, which could lead to sanctions.

The death of Hariri, a strong opponent of Syrian domination of Lebanon, transformed Lebanon”s political landscape. Syria pulled its troops from Lebanon after three decades. Damascus had gone into Lebanon to quell a civil war.