Washington - The biggest challenge to stabilising Afghanistan remains the sanctuaries in Pakistan that shelter militants fighting the US-led coalition, according to President Donald Trump’s nominee to lead allied forces in the 17-year-old war.

Ten months into the Trump-approved strategy that added as many as 4,000 American troops and approved more aggressive action against the Taliban, Pakistan’s actions remain “contradictory,” Army Lieutenant General Austin Miller told the Senate Armed Services Committee on Tuesday.

“We should have high expectations that they are part of the solution, not just diplomatically but from a security standpoint as well,” he said. In written answers, Miller said Pakistan has made “many sacrifices” and “its security forces have fought bravely,” but “we have not yet seen these counterterrorism efforts against anti-Pakistan militants translate into definitive actions against Afghan Taliban or Haqqani leaders residing in Pakistan.”

Miller said he still had “high expectations” for Islamabad in ending the Afghan war, but that better cooperation and coordination were needed. “It’s obviously a very tough neighbourhood with some tough neighbours,” Gen Miller told lawmakers. “Pakistan must be part of the solution, and we should have high expectations that they are part of the solution.”

Trump has been equally vocal in the past about Pakistan, saying in August that “we can no longer be silent about Pakistan’s safe havens for terrorist organisations, the Taliban and other groups that pose a threat to the region.”

Miller, 57, is a battle-hardened veteran who as a captain led a ground assault during the October 1993 “Black Hawk Down” fight in Mogadishu, Somalia, and was awarded the Bronze Star. He’s now head of the Joint Special Operations Command, the unit of elite US commando forces conducting counterterror operations in Afghanistan.

Miller, who appears headed for quick approval by the Senate, will be executing the Trump-backed Pentagon strategy that abandons any public timeline for withdrawing about 14,000 US troops and assigns them to work more closely to train and assist Afghan troops, down to combat-unit levels.

“The focus of military operations in 2018 is supporting secure and credible elections,” Miller said. “In 2019 and beyond, the improved leadership and increased offensive capability should result in improved battlefield performance to compel” the Taliban into political reconciliation, he said.

Miller said in his written answers that a ceasefire declared by Afghan President Ashraf Ghani -- and honoured by the Taliban for three days before they returned to combat - was “an unprecedented moment in this long war.”

Republicans and Democrats alike questioned Miller on what conditions have changed in 17 years of combat.

“Obviously there is an expectation that you’ll bring something in that is going to offer something new,” Senator James Inhofe told Miller. “Because to continue to do the same thing that’s led us into 17 years is not going to be acceptable.”

Senator Elizabeth Warren recounted several instances over the past several years when American commanders and Defence Secretary Leon Panetta touted great progress or “turning points.” The most recent claim was last year when the current commander, General John Nicholson, said “US and Afghan forces have turned the corner.”

“General Miller, we’ve supposedly turned the corner so many times that it seems we’re going in circles,” Warren said.

But Gen Miller wasn’t ready to proclaim any corners had been turned in Afghanistan. “I can’t guarantee you a timeline or an end date,” he said. “But I go back to the vital interests of national security for America. I know this [war] is having a [negative] effect on elements that would attack us.”

Gen Miller warned that a rapid drawdown of US or allied forces would likely produce the same chaotic situation that engulfed Iraq after the 2011 American military pullout there, clearing the way for the rise of Islamic State in Iraq and Syria.

“With a precipitous and disorderly withdrawal, we would see negative effects on US national security,” the general said. “I would be concerned about ISIS and Al-Qaeda’s ability to emerge” in the power vacuum left behind.

Meanwhile, Alice G Wells, Senior Bureau Official for South and Central Asian Affairs, said despite some positive indicators, the US has not yet seen Pakistan taking decisive steps that it would have expected to see ten months after the announcement of the South Asia strategy, including "arresting or expelling Taliban elements who will not come to the negotiating table."

Wells, who is scheduled to testify before the House Foreign Affairs Committee, said in her prepared statement ahead of her hearing that "Pakistan is on notice that we expect its unequivocal cooperation ending sanctuaries that the Taliban have enjoyed.” The US, she said, is engaging with all of Afghanistan's neighbours and near neighbours to build regional support for the Afghan government's peace vision and discourage spoilers.

Wells said Pakistan has an important role to play and has legitimate interests that it wants to ensure are met during any peace process. The dialogue that we have with Pakistan seeks to address those concerns while also encouraging additional concrete support for Afghan peace efforts, she said.

For example, with US support, Pakistan and Afghanistan entered into a constructive dialogue to develop the Afghanistan-Pakistan Action Plan for Peace and Solidarity (APAPPS), an initiative to which we have given our full support, she said.

Wells said all of Afghanistan's neighbours from Iran and Russia, to India, China, and the Central Asian states have repeatedly stated their support for an Afghan peace process. "All of these countries feel a strong stake in Afghanistan's future security and stability. They all would benefit from a political settlement in Afghanistan, which would help to reduce the terrorist and narcotics threat to their own citizens and also bolster regional economic cooperation," she noted.

According to Wells, after more than 17 years of war, there is a real opportunity this year to start an Afghan peace process that could lead to a durable settlement of the conflict. "Such a settlement would help secure vital US interests and ultimately reduce the costs associated with America's long-term engagement in Afghanistan," she said.

"The basis for our cautious optimism starts with the Afghan government, which under President (Ashraf) Ghani's strong leadership is doing everything possible to signal its openness to a dialogue with the Taliban, she said.

"More recently, President Ghani took another unprecedented step and announced a temporary ceasefire in offensive operations against the Taliban for the week surrounding the Eid holidays," Wells said. The Taliban responded with a three-day ceasefire. This was the first national ceasefire in the last 17 years of the Afghan conflict, and the national outpouring of relief and joy this past weekend was unlike anything Afghanistan has seen in many years, Wells observed in her written testimony.

According to Wells, recently, there have been signs that the Taliban's Pakistan-based leaders are debating the merits of joining a peace process. However, the group has not responded to President Ghani's offer of unconditional talks.