Rex Tillerson appeared to undermine Trump's message on Afghanistan

Thomson Reuters

Secretary of State Rex Tillerson holds a press briefing

President Donald Trump's message Monday night was that the US would "win" under his new strategy in Afghanistan.

But his secretary of state appeared to lay the ground Tuesday for a different outcome and downplayed the likelihood that the US would walk away from its longest war in history with a victory.

"You will not win a battlefield victory," Tillerson said in a message aimed at the Taliban at a Tuesday press conference. "We may not win one, but neither will you."

"So at some point, we have to come to the negotiating table and find a way to bring this to an end," Tillerson said, adding that the White House is taking a "regional approach" by working with India and expecting more from Pakistan.

Trump on Monday night did not provide many specific details about his plans for Afghanistan, including timetables or troop numbers.

Tillerson fell in line with Trump in that regard, saying the administration was not "going to signal an increase, decrease, timing, any of that. ... It will be driven by conditions on the ground."

Trump, however, played up the theme that the US would follow a winning strategy.

"When I became President, I was given a bad and very complex hand, but I fully knew what I was getting into: big and intricate problems. But, one way or another, these problems will be solved - I'm a problem solver - and, in the end, we will win," he said during a speech to military personnel in Virginia.

He added: "Our troops will fight to win. We will fight to win. From now on, victory will have a clear definition: attacking our enemies, obliterating ISIS, crushing Al Qaeda, preventing the Taliban from taking over Afghanistan, and stopping mass terror attacks against America before they emerge."

Senior White House officials have indicated that Trump has agreed to increase US troop presence in the war-torn country, but that he will leave those specifics to Defense Secretary James Mattis.

The US currently has about 8,400 US troops in Afghanistan and is expected to add about 4,000 more, as the longest running war in American history - going on 17 years - still has no end in sight.