US Deputy Secretary of State John Sullivan was speaking at a ministerial meeting of the Security Council at the UN headquarters in Afghanistan.
"We seek to work cohesively and effectively with Pakistan, but cannot be successful if the status quo, one where terrorist organisations are given sanctuary inside the country's borders, is allowed to continue," Mr Sullivan told the meeting.
"Stability and prosperity in Afghanistan will benefit Pakistan as well, since it will enable a return of refugees and remove the ability of ISIS and other terror groups to operate against Pakistan from outside the country," he said.
"This is why Pakistan should join our efforts to bring a resolution to the conflict, also as spelled out in our South Asia strategy," Mr Sullivan said.
Pakistan, he said, has suffered greatly from the effects of terrorism, and thus the country can and should be an integral partner in its shared efforts to achieve peace and stability within the region.
John Sullivan rued that the international community has thus far fallen short in providing that kind of unified support to the Afghanistan government. "We have even seen certain countries pursue counterproductive strategies that provide support to the Taliban in the name of countering ISIS. This approach is misguided, or worse, pernicious," he said.
"We can - and must - fight ISIS in Afghanistan, while ensuring the Taliban is forced to the negotiating table. Working closely with our Afghan partners, we have made significant progress against ISIS in eastern Afghanistan," Mr Sullivan said.
"Together, we have maintained persistent pressure on ISIS, significantly reducing its territory and eliminating one-third of its fighters. Supporting the Taliban only serves to prolong the conflict and foster an unstable and insecure environment, one that ISIS exploits to threaten Afghanistan and the broader region," the top American diplomat said.
"Ultimately, to defeat ISIS in Afghanistan - and prevent the group's spread across the region - each country at this table must be aligned in the strategy, and in their commitment to follow-through.
Ineffective strategies that enable insurgent groups must cease - instead, they need to join together and provide unwavering support for the Afghan government," he said.