Top US general Richard Myers has described the security situation in Afghanistan as "exceptionally good".
US commanders say the Taleban forces are "essentially in disarray"
The chairman of the Joint Chiefs of Staff was speaking during a visit to the capital, Kabul.
But his remarks came only a few hours after six people, including a US soldier, were killed by land mines.
Afghanistan is littered with land mines, the legacy of more than a quarter of a century of war.
The US has 17,000 troops in the country fighting insurgents of the Taleban, whose regime fell in late 2001.
"Security is very good throughout the country, exceptionally good," Gen Myers said after meeting Afghan President Hamid Karzai and US commanders in Kabul.
Gen Myers said the Taleban were "essentially in disarray" and could weaken further if a low-key initiative aimed at attracting "non-criminal Taleban" took off.
But the general's assessment did not include the ever-present threat from land mines.
One US soldier was killed and four wounded when a military patrol drove over a land mine near the US base in the western Afghan town of Shindand.
US spokesman Maj Steve Wollman said a vehicle carrying Afghan civilians - apparently curious to watch the American rescue operation - struck another mine nearby, killing five people and injuring six.
Meanwhile, one Afghan soldier died on Tuesday when he hit a mine during a search for bodies from last month's crashed airliner, officials said on Wednesday.
Mines and unexploded ordnance litter Afghanistan and move around in the spring because of melting snow and heavy rainfall, say correspondents.
But irrespective of such hurdles, Gen Myers was upbeat during his brief meeting with the media at Kabul airport.
He said the US was considering establishing long-term bases in Afghanistan as part of its "global basing construct" - a strategy aimed at establishing US security presence across the world.
But he has yet to advise US President George W Bush on having a permanent US military base in Afghanistan, he said.
"But clearly we have developed good relationships and good partnerships in this part of the world, not only in Afghanistan," Gen Myers said with reference to existing US bases in Uzbekistan and Kyrgyzstan.
The Afghan government says it wants a "strategic partnership" with the US, but has so far said nothing about permanent US military bases in the country.
The US troops are the main component of the international coalition force in Afghanistan.
Their focus is searching for members of al-Qaeda and fighting the Taleban-led insurgency that still affects much of the south and east.