* Western stance on missiles helps Assad-Alkhatib
* Says will still work for opposition unity
* Appeals for military support for rebels (Adds quotes, bylines)
By Yara Bayoumy and William Maclean
DOHA, March 27 (Reuters) - The refusal of international powers to provide Patriot missile support for rebel-held areas of northern Syria sends a message to President Bashar al-Assad to "do what you want", Syrian opposition leader Moaz Alkhatib said on Wednesday
Alkhatib, a popular figure in the opposition, also said he would not rescind his resignation as leader of the main anti-Assad alliance but he would still perform leadership duties for the time being.
NATO said on Tuesday it had no intention of intervening militarily in Syria after Alkhatib said he had asked the United States to use Patriot missiles to protect rebel-held areas from Assad's air power.
"Yesterday I was really surprised by the comment issued from the White House that it was not possible to increase the range of the Patriot missiles to protect the Syrian people," Alkhatib told Reuters in an interview.
"I'm scared that this will be a message to the Syrian regime telling it 'Do what you want'."
Asked about his resignation on Sunday as leader of the rebel coalition - which he has said was motivated mainly by frustration at Western reluctance to increase support for the opposition - he said: "I have given my resignation and I have not withdrawn it. But I have to continue my duties until the general committee meets."
Alkhatib took Syria's vacant seat at an Arab League summit in Qatar on Tuesday, deepening the Assad government's diplomatic isolation two years into a conflict that has cost an estimated 70,000 lives.
The 22-nation League lent its support to giving military aid to the Syrian rebels and a summit communique also offered some of its sternest language yet against Assad, affirming member states had a right to offer help.
But Tuesday's proceedings offered no clarity on Alkhatib's position in the leadership, a question central to Arab and Western efforts to shore up the political credibility of the opposition and heighten pressure on Assad and his inner circle.
In his remarks to Reuters, Alkhatib sought to portray himself as a conciliatory figure, declining to be drawn on his next political moves.
Asked whether he would withdraw his resignation, he replied: "This is the situation as it stands."
He said that until the coalition meets, he would focus on "narrowing differences and building a bridge between the factions in the opposition".
Opposition rifts are many. They include rivalry between liberals and various sorts of Islamists, between exiles and groups that operate within Syria, and between those seeking a political settlement and those who insist an armed campaign is the only solution.
Those divisions are reflected among Arab states, which agree on little other than their professed abhorrence of the bloodshed caused by an increasingly sectarian conflict.
Alkhatib's decision to quit, which he blamed on the world's failure to back the armed revolt, also appeared to be motivated by internal disputes in the alliance. It undermined the alliance's claim to provide a coherent alternative to Assad.
Liberals saw it as a protest against what they view as the rising influence of hardline Islamists in the Qatari-backed umbrella group set up in Doha in November
On Wednesday, Alkhatib indicated irritation with the efforts of outside powers to influence the course of the rebellion.
"This is a game that the Syrian people are now used to. They say 'do this and we'll help you, do that and we'll help you," he said, without naming individual countries.
But he also sought to play down internal differences within the coalition.
"The most distinguished parliaments in the world have differing points of view. That's normal. There are lots of different point of view. We have already come up against some obstacles and we have overcome them." (Additional reporting by Regan Doherty; Editing by Angus MacSwan)