UNITED NATIONS – German investigator Detlev Mehlis, who has been very tough on Syria in his probe of the Hariri assassination, may soon be replaced by another team leader, a senior U.N. official, Ibrahim Gambari, said yesterday.

Mr. Gambari, who is Secretary-General Annan’s top political aide, told reporters that the independent investigation established by the U.N. Security Council in the aftermath of the February car bombing that killed the former Lebanese prime minister, “has to continue” past its December 15 deadline. According to several U.N. sources, Mr. Mehlis has indicated that for personal reasons he may be unable to head the team into the future.

“I don’t think he sees himself as continuing ad infinitum,” Mr. Gambari said, adding that the investigation will go on “with or without Mehlis.” He said that “it is very clear he will need an extension [and] the Lebanese government says it is now ready to approve an extension.”

France and America, which are leading the Security Council efforts on Lebanon, as well as Mr. Annan, may now need to find a new investigator. “He is doing a really great job,” French ambassador Jean Marc de-la Sabliere told The New York Sun yesterday, referring to Mr. Mehlis. When asked if he was concerned that a replacement might not be as tough as the German investigator, he said, “We don’t really know.”

“What we did was create an independent international investigatory commission,” American ambassador John Bolton said. “That commission will continue. Whether it would be Mr. Mehlis or someone else is a subject we could address later.”

Syria has tried to discredit Mr. Mehlis’s findings. On Sunday, national television broadcast one of the witnesses that the U.N. investigators relied on, Hosam Taher Hosam, recanting his testimony. Yesterday, Mr. Hosam said that his family in Lebanon is in danger.

Last week, another witness who was mentioned in the Mehlis report was found dead on a mountain road northeast of Beirut, in what was ruled as a car accident, according to the Associated Press. And yesterday a former military intelligence chief, Raymond Azar, who was one of the Syrian officials Mr. Mehlis wanted to interview, was rushed from jail to a hospital with heart problems.

Mr. Mehlis, named last May by Mr. Annan and approved by the council, has surprised diplomats who are accustomed to less aggressive U.N. investigators. Turtle Bay officials, however, tried to minimize any damage the investigation might cause, and prevent any significant change in the Baathist rule of Syria. “We don’t want another Iraq,” Mr. Annan last week told a meeting of a large U.N. voting bloc known as “the group of 77.”

The German investigator has steered clear of politics, concentrating instead on police work. In his report, he named as suspects some of Damascus’s most senior officials, including President al-Assad’s brother, Maher, and his brother-in-law, Assef Shawkat. Mr. Annan tried to tone down that report, deleting the names of several Syrian officials from a draft that was nevertheless mistakenly given to diplomats.

Mr. Annan later mediated between Mr. Mehlis and the Syrian government, and an agreement was reached to conduct interviews with Damascus officials in Vienna. Mr. Gambari said yesterday that the interviews will take place between next Monday and Wednesday.

That would leave the investigating commission just enough time to submit its next report, due on December 15. If the investigation is not complete by then, however, it may be difficult to convince Mr. Mehlis to continue, as he has expressed privately his wishes to return home, according to two U.N. sources.

In a closed consultation session of the council yesterday, Mr. Bolton asked Mr. Gambari if he had weighed the pros and cons of his meeting during a Middle East trip with top Hezbollah officials. Hezbollah is considered a terrorist organization by the State Department.

Mr. Bolton told the Sun that he asked “whether or not it’s appropriate for the U.N. to consult with Hezbollah.” Mr. Gambari, he added, “said he thought that it was, so we now will consider his answer.”

Mr. Gambari’s Hezbollah meetings took place two days before the Shiite group began shelling Israeli towns. Yesterday Mr. Gambari told the Sun that in the meetings he raised the Security Council demand for Hezbollah to disarm. He said the government of Lebanon was “happy” that he conducted the meetings. According to diplomats who attended the council meeting, Mr. Gambari reminded Mr. Bolton that an American ambassador, Andrew Young, lot his job after meeting with Yasser Arafat.