After eight years of war in Afghanistan, an initial report about a new push by President Barack Obama to replace the Taliban with a new government within the next 18 months is reassuring, U.S. Senator Carl Levin said on Monday.

A little over a week ago, 15,000 troops from a NATO-led coalition, along with a significant number of Afghan Troops, launched a major new offensive in southern Afghanistan.

The new assault's name - which in the local language means together - is called Operation Moshtarak.

Sen. Levin, who heads a Senate armed services panel, asked U.S. military strategic director Lieutenant General John Paxton about how Afghan forces were doing in the operation.

Their physical presence is more than ours, Paxton testified. While he had not seen activity in person he said every indication is that sometimes they are in the lead.

Paxton said Afghan troops had the willpower, bravery and willingness to do so.

Your report is a good one and reassuring, Levin told him.

Prior to testimony, Sen. John McCain (R-Ariz.) said members of the panel should refrain from drawing overly positive or negative conclusions from the progress of the operation so far.

We shouldn't expect to see the results we need overnight, he said. 'Hold' and Build' phases will determine the overall success. We expect this uneven process.

McCain challenged another witness, US Undersecretary of Defense Michele Flournoy, to accept that Dutch troops would be withdrawing after the collapse of their government, taking nearly 2,000 troops with them.

Flournoy said she expected that there would be some significant contribution that would remain when a new Netherlands government comes to power.