* US to host talks between Afghanistan, Pakistan
* Karzai due to take part, Kerry to chair (Adds Rasmussen quotes)
Pakistan must crack down on militants who use the country as a sanctuary to launch attacks in Afghanistan, the head of NATO said on Tuesday, before a U.S.-chaired meeting that will try to ease friction between the neighbours.
U.S. Secretary of State John Kerry will host talks between Afghan President Hamid Karzai and senior Pakistan officials in Brussels on Wednesday, with the aim of calming tension over border disputes and a stalled peace process.
"It is a problem that terrorists can cross the border, conduct terrorist acts in Afghanistan and then seek sanctuaries, safe havens in Pakistan," NATO Secretary-General Anders Fogh Rasmussen told reporters after alliance foreign ministers met to discuss Afghanistan.
"It is countering all our efforts to improve the security situation. So we have a common interest in an intensified fight against these cross-border activities," he said.
NATO had urged Pakistan's government and military to step up efforts to fight militants in the border region, Rasmussen said.
"We need a positive engagement of Pakistan if we are to ensure long-term peace and stability not only in Afghanistan, but in the region."
Afghan officials say Pakistan has a long history of supporting Afghanistan's Taliban and other insurgent factions. Pakistan has in turn accused Afghanistan of giving safe haven to militants on the Afghan side of the border.
Afghanistan has grown increasingly frustrated with Pakistan over efforts to pursue a peace process involving the Taliban, suggesting that Islamabad is intent on keep Afghanistan unstable until foreign combat forces leave at the end of 2014.
The talks follow weeks of tension with Pakistan over their 2,600 km (1,600 mile) border and stalled peace efforts.
U.S. officials hope that Kerry, who has a good relationship with Karzai, can bring the parties back to the negotiating table and make constructive progress on an issue that has long-term security implications for Washington.
Rasmussen held talks with Karzai at NATO headquarters on Tuesday, which he said focused on the legal framework for NATO's presence in Afghanistan after 2014.
NATO-led forces are expected to cede the lead role for security in Afghanistan this spring to Afghan soldiers, 12 years after the United States invaded Afghanistan to oust the Taliban government harbouring Osama bin Laden, the al Qaeda leader.
The White House has yet to decide how many U.S. troops will remain in Afghanistan after 2014. Much depends on progress in negotiations with Karzai on a Bilateral Security Agreement to define the future legal status of U.S. forces.