WASHINGTON (Reuters) - The top U.S. commander in Afghanistan said on Thursday that there was a need for a “holistic review” of the relationship with Pakistan, potentially opening the door for a new approach to one of America’s most vexing alliances.

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Experts said the remarks by Army General John Nicholson, who leads U.S. and international forces in Afghanistan, could signal a harsher policy toward Pakistan under President Donald Trump’s administration.

However, they warned that such an approach could be a high-risk strategy that could threaten the long-term stability of the region.

“Our complex relationship with Pakistan is best assessed through a holistic review,” Nicholson told the Senate Armed Services Committee.

He added that ties with Pakistan would be a priority in his discussions with U.S. Defense Secretary James Mattis and the White House, which has given little details on its strategy in Afghanistan and Pakistan.

The United States has cut both military and economic aid to Pakistan sharply in recent years, reflecting mounting frustration among a growing number of officials with the country’s support for the Taliban in neighbouring Afghanistan.

“The tools that will get Pakistan to hurt so badly, that it would want to do what the U.S. is asking, is a very high-risk proposition in terms of what happens within Pakistan,” said Moeed Yusuf, the associate vice president of the Asia Center at the United States Institute of Peace.

Yusuf said the review would likely lead to a harsher U.S. policy toward Pakistan and could include looking at reducing the level of economic assistance and military support, increasing the number of drone strikes along the border between Afghanistan and Pakistan, and sanctions against Pakistani individuals.

“U.S. policy makers, deep down inside, they realise Pakistan is more important than Afghanistan in the long term,” Yusuf said.

A report released earlier this week from the Hudson Institute, a Washington-based think tank, called for a new U.S. approach to Pakistan with the Trump administration making it “more and more costly for Pakistani leaders to employ a strategy of supporting terrorist proxies to achieve regional strategic goals.”

Nicholson’s comments on Pakistan come as Afghan government forces control no more than two-thirds of national territory, and have struggled to contain the Taliban insurgency since the bulk of NATO soldiers withdrew at the end of 2014.