Lakhdar Brahimi knew what he was getting into. His mission: Find a solution for negotiating the Syrian conflict. His chances for success: little to impossible. His predecessor Kofi Annan failed - none of the parties in Syria involved in the conflict were willing to negotiate.

But Brahimi wasn't daunted. In September last year, the 79-year-old Algerian took over as the UN-Arab League's Joint Special Representative for Syria. Annan had stepped down - frustrated - after just six months in this position.

Another frustrated negotiator

Now, though, Brahimi also wants to pack it in. The former Algerian foreign minister is about to hand in his resignation, according to UN sources quoted by several news agencies.

Brahimi was "itching to resign but being persuaded to hang on for a few more days," one UN Security Council diplomat told AFP.

UN Secretary-General Ban Ki-moon, US Secretary of State John Kerry and representatives from other permanent members of the Security Council want to sway Brahimi to continue his work. But the odds of success are slim.

"He has told everyone that he wants to leave, there is little hope that he will stay," an Arab diplomat at the UN told AFP. The Dubai-based broadcaster Al Arabiya reported that Brahimi had in the meantime agreed to stay on until the end of May. His resignation would be a further blow for efforts to reach a peaceful solution to the Syrian conflict.

Falling short of the peaceful target

"Lakhdar Brahimi noticed in the past few months that he could not implement his goals and his notions of a possibly quick peaceful solution in Syria," said Sebastian Sons, Syria expert at the German Orient Institute in Berlin. Brahimi is apparently disillusioned.

"He has probably come to the conclusion that the entire matter no longer has any chances of success," Sons told DW.

Brahimi is the Joint Special Representative for both the UN and Arab League. But while Secretary-General Ban consistently calls for talks and objects to any weapons being supplied to the conflicting parties, some members of the Arab League are supporting the Syrian opposition with money and arms.

In addition, the Arab League in March decided to recognize the opposition Syrian National Coalition as the legitimate government of Syria - leading President Bashar al-Assad to terminate any further consultations with Brahimi. According to diplomatic circles in New York, he was under the impression that the Arab League was going down a very different path than the UN - putting him in a futile position.

"He (Brahimi) has been trapped between the Syrian regime, which has treated him contemptuously, and the Sunni Arab governments that don't want to compromise with Assad," said Richard Gowan of New York University's Center on International Cooperation. "He deserves credit for persevering as long as he has."

UN is blocked

But the UN is also blocked in the Syria crisis. Russia's veto in the Security Council is preventing a tougher line of action against the Assad regime. China is skeptical toward stricter measures, as well.

"The point was missed at which Russia should have been made an offer to move it to change its opinion in the UN Security Council," Sons said. Assad's resignation had been demanded from the very beginning. But the leeway for negotiation has become extremely narrow.

In any event, large parts of the Syrian opposition refuse to negotiate with the Assad regime. The president himself is eyeing a military solution.

"Assad is playing for time because he has clearly realized how the international community is at odds," Sons said. The perspectives for a solution at the negotiating table, says Sons, are "minimal." He believes the conflict could still continue for months, if not for years - even a successor to Brahimi would not be able to change this.

The option of international intervention is still open - without approval of the UN Security Council. Syria expert Gowan said Brahimi's resignation could increase pressure on US President Barack Obama to take a tougher stance against Assad.

"President Obama is already under pressure to react forcefully to the reports that the Syrian army has used chemical weapons," Gowan said. "Obama's critics will inevitably argue that Brahimi's exit proves that there is no chance of a diplomatic solution left, and it's time to intervene."

However, for now, Obama is still reluctant to embark on a military adventure in Syria.