After two assassination attempts that bear the markings of Al Qaeda, the US government is stepping up efforts aimed at protecting Pakistan’s president, Gen. Pervez Musharraf, and urging him to crack down further on Islamic terror groups, US officials said.The US had sent electronic jamming devices that helped foil the first attempt on Musharraf by interfering with the detonation of explosives. Since the attacks, the US has increased intelligence sharing and other efforts to help Musharraf’s security forces, although it is not providing bodyguards, a step taken to safeguard Afghanistan President Hamid Karzai. FBI officials in Pakistan are helping probe the attacks. Musharraf’s longevity and stability and the cooperation of Pakistan are critical to the US effort to capture or kill Osama bin Laden and Al Qaeda operatives. If Musharraf were to die in an attack, US officials said they believe the Pakistani army would move to appoint a successor — with the most likely candidate being the Army Vice Chief of Staff, Gen. Muhammad Yousaf Khan, viewed by US officials as pro-American and likely to continue Musharraf’s prosecution of Al Qaeda. ‘‘My assumption is the army will assert itself and shove the civilians into the background’’ if something happened to Musharraf, said Teresita C. Schaffer, former ambassador to Sri Lanka. ‘‘There is a very strong suspicion that the Al Qaeda was involved in the attacks,’’ a US intelligence official said. One of the assailants is believed to be Muhammed Jamil, who fought with the Taliban during Musharraf’s cooperation after 9/11 and the US-led war in Afghanistan gave the CIA and US military the opening — and political cover from Congress, which had restricted military ties with Pakistan for the last 10 years — to dramatically increase ties. — (LAT-WP)