ISLAMABAD - Top US military commander Admiral Mike Mullen on Wednesday asked Pakistan to take more concerted action against militants beyond the lawless tribal regions and investigate aggressively any possible link of these groups to Mumbai attacks. Admiral Mullen, the Chairman of the US Joint Chiefs of Staff, while noting recent success by Pakistan Armed Forces against extremists in the border regions, urged the top political and military leadership of Pakistan to take more and more stern action against the militant extremists elsewhere in the country. According to a press statement issued by the US Embassy, the American military official held meetings with President Aif Ali Zardari, National Security Advisor Mahmood Durrani, Chief of the Army Staff, General Parvez Ashfaq Kayani, Chairman of the Joint Chiefs of Staff Committee, General Tariq Majid and Director General of Inter Services Intelligence (ISI) Lt General Ahmad Shuja Pasha. He urged Pakistan to investigate aggressively any possible links of groups based in Pakistan to the Mumbai attacks. Admiral Mike Mullen, who arrived here Wednesday, in his talks with Pakistani leaders "urged them to investigate aggressively any and all possible ties to groups based in Pakistan," the US embassy said in a statement. He said, "All agreed that the tragedy in Mumbai represents a dangerous escalation in the sophistication of extremist attacks and an increased threat to the entire region." The mounting tension between Islamabad and New Delhi has increased worries not only in Washington but also other world capitals like London, Paris and Berlin, etc. The US Secretary of State Condoleezza Rice, who spent a busy day in New Delhi Wednesday discussing Mumbai attacks and their impact on Indo-Pak relations, will arrive here today (Thursday) to have talks with Pakistani leadership. The visit of Dr Rice and that of Admiral Mullen is part of international efforts to defuse the Indo-Pak crisis arising out of the Mumbai attacks. The US is worried that any possible conflict between Islamabad and New Delhi would only help the international terrorists network and would have negative impact on the ongoing global war on terror. An official desiring not to be named said that during the meeting with Admiral Mullen, the President said that Pakistan strongly condemned Mumbai blasts, saying that Islamabad was ready to help New Delhi in its investigation into the Mumbai carnage. He said that Pakistan had no hand in the ghastly act of terror in Indian financial capital, adding that all allegations being levelled in this regard were baseless.