The cabinet decided on the boycott to protest against the deadliest cross-border strike by NATO troops in 10 years of war in Afghanistan that has plunged the uneasy US-Pakistani alliance into perhaps its deepest crisis. But Prime Minister Yousuf Raza Gilani appeared to hold out the possibility of conditions, briefing reporters on a call made by Afghan President Hamid Karzai asking him to reconsider. "I replied that the territory of Afghanistan was being used against Pakistan and he said it was done by NATO and I told him to talk to the US about it. "I told him that we have to protect our country and work for its security and defence. If we go to Bonn for you then who will guarantee our security? We cannot just go like this if someone will not ensure our security," he added. In a conversation with German Chancellor Angela Merkel, Gilani also refused to send his foreign minister, but said a parliamentary committee on national security would decide whether Pakistan's ambassador to Germany would attend. Pakistan has closed the Afghan border to NATO, a lifeline for 140,000 foreign troops in Afghanistan, ordered US personnel by December 11 to leave Shamsi air base reportedly used by CIA drones and launched a review of the alliance. "Shamsi air base will be closed after December 11," Defence Minister Ahmed Mukhtar told reporters in Islamabad. Yet the precise sequence of events is disputed. Islamabad insists the air strike was unprovoked, even a deliberate act of aggression. Afghan and Western officials have reportedly accused Pakistani forces of firing first. Protests continued for a fifth day with up to 1,000 government loyalists demonstrating in Karachi, chanting "down with America, down with NATO, long live (army chief Ashfaq) Kayani, long live (President Asif Ali) Zardari." But she stopped short of apologising, as recommended by a key US senator -- should an official investigation show that the strikes were a mistake. "I'm one who believes that, if we made a mistake, we should admit it, we should apologise," Dianne Feinstein, a Democrat from California, told AFP.