WASHINGTON (AFP) - The US military has launched a coordinated operation with Pakistani forces to put pressure on insurgents on both sides of Afghanistan's wild eastern frontier, a US military commander said Tuesday. Dubbed "Operation Lionheart", the operation takes cooperation between US, Afghan and Pakistani forces to "the next level" in terms of intelligence sharing and coordination, said Colonel John Spiszer. "We are in coordination on a daily basis with the Frontier Corps," said Spiszer, who commands the 1st Infantry Division's 3rd Brigade. The Frontier Corps has been engaged over the past two months in fighting in Bajaur, which borders Afghanistan's Kunar province. Admiral Michael Mullen, the Chairman of the Joint Chiefs of Staff, said Monday that the Pakistani operations in Bajaur have had a "significant impact." Spiszer said his troops were working along the Kunar River valley and up into the mountain passes along the border to intercept and ambush insurgents trying to escape from Pakistani operations in its Bajaur Agency. "What we have done is worked very hard to refocus our ISR assets, intelligence, surveillance, reconnaissance assets to do everything we can to identify transiting across the border," he said. Spiszer, who has about 3,000 US troops in an area that encompasses four Afghan border provinces, said he did not have enough troops but would get more with the arrival of a brigade from the 10th Mountain Division early next year. He hailed the cooperation developing between the US and the Pakistan military as a major success. "I wish I had more resources to devote to it. And we will have more over the coming months," he said in a teleconference from Afghanistan. Meanwhile, NATO troops in eastern Afghanistan fired 20 artillery rounds at insurgents inside Pakistan after coordinating with Islamabad, officials said Tuesday. The military alliance said it fired the rounds after insurgents attacked its troops in Afghanistan's eastern Paktika province with rockets from across the border on Sunday. "The artillery fire caused a secondary explosion at the rocket launch site, which indicates additional munitions in the location," the NATO statement said. The Pakistani military confirmed the two sides coordinated in an attack on insurgents in Pakistan but provided no other details. Officials say relations between NATO-led troops in Afghanistan and Pakistan's military are improving. However, Pakistan has been complaining about unilateral missile strikes conducted by US forces into its tribal areas. Pakistani officials say the US strikes violate their country's sovereignty. Meanwhile, ISPR has strongly denied the statement of a US Commander regarding joint operation at Pak-Afghan border. Major-Gen Athar Abbas strongly refuted the statement and said that no joint operation was being carried out, and both the forces were conducting operations in their respective areas. "Pakistan forces are only allowed to take operation in Pakistani areas while US and Afghan forces conduct their own operations in the Afghan areas", he added.