* Iran envoy: Pakistan helped on Jundollah leader's arrest
* Iran-Pakistan; Pakistan-India; signs of easing tensions
* Any Afghan region cooperation unlikely to follow US script
By Myra MacDonald
LONDON, Feb 24 Iran's arrest of the leader of the Jundollah rebel group, possibly with help from Pakistan, is the latest sign of new cooperation among Afghan regional players positioning themselves for an eventual U.S. withdrawal.
Islamabad's ambassador to Tehran Mohammad Abbasi said on Wednesday Pakistan had helped Iran capture Abdolmalek Rigi, leader of the Sunni rebel group blamed for bombings in Sistan-Baluchistan province, bordering Pakistan and Afghanistan.
"I should say that his arrest could not happen without Pakistan's help," Abbasi told a news conference in Tehran, without giving further details.
Iran's accusations that Jundollah operated from bases in Pakistan's Baluchistan province have been a cause of friction with Islamabad and Rigi's arrest -- in circumstances yet to be fully explained -- could go some way to easing tensions.
Pakistan and Iran, which have also competed for influence in Afghanistan, have been trying to improve relations recently as regional players prepare for U.S.-led forces to start withdrawing in 2011.
"While Islamabad is cooperating with the United States, it must also balance those interests with its need for help from its neighbour, Iran, which, like Pakistan, understands it will be dealing with Afghanistan long after the United States has left," the STRATFOR global intelligence group said.
Pakistan and India, whose hostility has been exacerbated by deep distrust of each other's involvement in Afghanistan, are due to hold talks on Thursday to try to break a diplomatic freeze which followed the November 2008 attack on Mumbai.
Pakistan accuses India of using its growing presence in Afghanistan to support Baluch separatists -- who operate independently of Jundollah -- in its Baluchistan province. India denies this, saying it is funding development in Afghanistan.
India, Iran and Russia supported the then Northern Alliance against the Pakistan-backed Taliban when they were in power in Kabul from 1996-2001.
Western security analysts have long talked of the need for a regional settlement on Afghanistan to prevent a resurgence of old rivalries which could stoke a renewed civil war -- or even a de facto partition -- when U.S.-led troops begin to leave.
Any signs of renewed cooperation, between Pakistan and Iran, and between Pakistan and India, would go some way towards achieving this -- with the caveat that no country is likely to follow the U.S. script as its looks out for its own interests.
Tehran, locked in a showdown with the United States over its nuclear programme, has little reason to cooperate with Washington in helping it stabilise Afghanistan.
And many analysts saw Pakistan's arrest this month of Taliban commander Mullah Abdul Ghani Baradar in Karachi as an attempt to assert its own influence over any peace negotiations.
Baradar was described by some as a potential go-between in talks between the Taliban and either Afghan President Hamid Karzai or even the United States which might have circumvented Pakistan, where many Taliban leaders are believed to be based.
His arrest "has damaged the trust-building necessary for the preparation of talks and raised suspicions about the role of Pakistan", said one security analyst.
DETAILS ON RIGI'S ARREST MAY SHED MORE LIGHT
There have been contradictory reports about how Iranian security forces detained Jundollah leader Rigi, whose group had claimed an Oct. 18 bombing that killed more than 40 Iranians, including 15 from the elite Revolutionary Guards.
Intelligence Minister Heydar Moslehi said Rigi had been arrested on board a plane flying between Kyrgyzstan in Central Asia and Dubai. Television pictures showed him being taken off a plane in handcuffs, accompanied by four masked men.
Pakistan's ambassador promised more details about Rigi's arrest and Pakistan's help in the coming days -- something which should shed clearer light on how both countries are working together on Afghanistan.
Pakistan says it wants stability in its western neighbour but denies that it is seeking to reinstall the Taliban in power Kabul, saying that it does not want a "Talibanised" Afghanistan.
Its attitude to the movement it once backed has changed after a wave of bombings from its own Pakistani Taliban.
"As long as that pre-9/11 nexus between India, Iran and Russia is not revived, we don't want to play favourites. A neutral Afghanistan suits us fine," said one Pakistani source, speaking on condition of anonymity.
But it is also determined to prevent its old rival India from using Afghanistan to destabilise Pakistan.
India, with bad memories of Afghanistan being used as a base by Kashmir-focused militant groups when the Taliban were in power, is equally determined to ensure the country does not return to its state before the Sept. 11, 2001 attacks.
The foreign secretaries, or top diplomats, of the two countries meet in New Delhi on Thursday to find a way back into talks in which Afghanistan is likely to figure prominently.
Russia, meanwhile, whose 1979-1989 occupation of Afghanistan ended in disaster, is concerned both about any resurgence of the Taliban which might destabilise the Central Asia republics on its periphery and looking for a clampdown on the booming heroin trade which is killing thousands of its people.
"I can responsibly say that in the case of NATO's defeat in Afghanistan, fundamentalists, inspired by this victory, will set their eyes on the north," Russia's NATO envoy Dmitry Rogozin said last month.
"First they will hit Tajikistan, then they will try to break into Uzbekistan ... If things turn out badly, in about 10 years our boys will have to fight well-armed and well-organised Islamists somewhere in Kazakhstan," Rogozin said. (Additional reporting by Parisa Hafezi in Tehran and Gleb Bryanski in Moscow; Editing by Louise Ireland)