By MATTHEW ROSENBERG

ISLAMABAD -- The Islamist militant group behind the deadly attack in Mumbai one year ago remains a potent force determined to strike India and the West, and a source of acrimony between South Asia's nuclear-armed rivals, say officials and members of the militant faction.

Indian officials and experts say at least six new plots against Mumbai by the Pakistan-based group, Lashkar-e-Taiba, have been disrupted in the 12 months since 10 gunmen wrought three days of havoc on India's financial capital, killing 166 people.

Lashkar's infiltration of India's part of Kashmir is again on the upswing, the officials say; and a U.S. citizen with alleged ties to Lashkar was recently arrested in Chicago, evidence of the group's reach, U.S. officials say.

"Our aims are the same today as they were 10 years ago," said a man who identified himself as a former Lashkar militant now working with its charity arm. "We are waging war on the enemies of Islam."

U.S. officials and experts say hitting India remains the primary focus for Lashkar, which was nurtured in the 1990s by Pakistan's Inter-Services Intelligence agency for use as a proxy against Indian forces in the divided Himalayan region of Kashmir. Pakistan banned the group in 2002 and officials here say they cut ties with it at the time.

But no one disputes that Lashkar continued to operate from Pakistan, repeatedly striking Indian targets in recent years. Another Mumbai-style attack, say officials from both countries, risks sparking a fourth war between the neighbors.

At the very least, Lashkar's continued existence presents a major obstacle to peace between the rivals. The tension also jeopardizes U.S. efforts in Afghanistan by keeping the bulk of Pakistan's sizable army focused on India, not the Taliban, say U.S. officials.

Yet Lashkar endures today because Pakistan's pledges to dismantle it in the wake of the Mumbai attack remain largely unfulfilled, say U.S., Indian and some Pakistani officials.

The group's long ties to Pakistan's powerful security establishment and the deep roots it has put down in towns and villages through its charity arm leave the government with a difficult challenge. Many Pakistanis still doubt Lashkar's role in the attack, and officials here privately say they fear a popular backlash if they move too forcefully against the group.

Timeline

* Nov. 26, 2008: 10 men from the Pakistan-based militant group Lashkar-e-Taiba begin a gun-and-grenade assault on targets in Mumbai, lasting nearly three days and leaving at least 174 people dead.
* Dec. 11, 2008: Pakistan moves against Jamaat-ud-Dawa, the charity front of Lashkar, arresting the group's leaders and shuttering its offices a day after the U.N. sanctioned the group. Days earlier, Pakistan also began arresting suspected members of Lashkar.
* Jan. 5, 2009: India gives Pakistan its first dossier of what it says is evidence that Lashkar orchestrated the Mumbai attack. The two countries have since repeatedly exchanged additional dossiers, although each side has complained about the information provided by the other.
* Jan. 6, 2009: After weeks of denials, Pakistan acknowledges that the single gunmen captured by Indian police in Mumbai, Mohammed Ajmal Kasab, is a Pakistani citizen.
* Feb. 12, 2009: Pakistan publicly acknowledges for the first time that the Mumbai attack was partly planned on its soil and says it has arrested most of the key plotters, including the alleged operations chief of Lashkar, Zaki ur-Rehman Lakhvi.
* June 2, 2009: A Pakistani court orders the founder of Lashkar, Hafiz Mohammed Saeed, released from house arrest, finding that the government does not have enough evidence to hold him. Mr. Saeed maintains that he runs a charity, nothing more.
* July 20, 2009: The single attacker captured by Indian police, Mohammaed Ajmal Kasab, confesses in open court that he took part in the assault. He says he was trained by Lashkar in Pakistan.

Pakistani officials also worry about taking on a potent enemy as they are trying to beat back the Taliban, which has killed hundreds of people in terrorist attacks in Pakistan since early October.

U.S. officials and analysts also say factions within Pakistan's military still see Lashkar as a potential weapon to be used in any future conflicts with India. Lashkar "has historically been Pakistan's most reliable proxy against India and elements within the military clearly wish to maintain this capability," according to a report this week by security analyst Stephen Tankel in the CTC Sentinel, published by the Combating Terrorism Center at the U.S. Military Academy at West Point.

Pakistan, following India and the U.S., concluded in the weeks after the Mumbai attack that it was carried out by Lashkar. Islamabad moved against the group, arresting dozens of people and banning its charity wing, Jamaat-ud-Dawa.

But most of those arrested have since been released and the trial of seven still-jailed Lashkar suspects, including the group's alleged chief of operations, has been repeatedly delayed.

U.S. officials, experts and Lashkar members say the group's few thousand fighters are still training at camps and safe houses, many of them in Pakistan's part of Kashmir.

Money is still flowing into its charity arm, which is now operating under a new name, Falah-i-Insaniat, according to Western officials and members of the group. The charity is best known for aiding victims of the 2005 earthquake and refugees from a Pakistani army offensive against the Taliban in the Swat Valley this year.

India and Pakistan have exchanged a series of dossiers detailing what they know about the attack's planning and execution, but each side complains the information provided by the other is insufficient.

Pakistani officials, for example, say India hasn't given them enough evidence to try Lashkar's founder, Hafiz Mohammaed Saeed, who has been in and out of house arrest since the attack. On Friday, Mr. Saeed preached a sermon to thousands of followers at the Jamia al Qadisa Mosque in the eastern city of Lahore.

"No power on the earth can defeat Muslims if they follow the God's path," preached Mr. Saeed, who says he runs a charity, and nothing more. "You can see what has happened to the American forces in Iraq and Afghanistan."

Pakistani officials say the men awaiting trial are the key players in the group, especially the alleged operations chief, Zaki ur-Rehman Lakhvi.

"Pakistan's political and military leadership endeavors to bring all terrorists, including those involved in Mumbai attack, to justice.... Any reports to the contrary are false and misleading," said Farahnaz Ispahani, a spokeswoman for Pakistani President Asif Ali Zardari. "The least we seek from the international community is recognition of our struggles."

U.S. officials say Pakistan's civilian leadership -- especially President Zardari and Prime Minister Yousuf Raza Gilani -- remains committed to dismantling Lashkar. They are far less certain about Pakistan's military and its spy agency, the ISI. Both deny aiding Lashkar.

An ISI officer said "maybe a handful" of retired officers work with Lashkar. The officer said the agency maintains informal contacts needed to monitor the group.

The officer added that Pakistan is facing multiple Taliban attacks every week and has to prioritize when it comes to moving against militants. "Which choice do you think we should make? Defend ourselves or defend India?" he said.
—Zahid Hussain in Lahore contributed to this article.