US Ambassador to Afghanistan Ryan Crocker said that America will not have permanent military bases in Afghanistan, nor will it ever use the embattled nation to launch offensives on another state.

Crocker sought to reassure Afghans and the region at a Kabul press conference that the long-term agreement between the two countries, signed Wednesday, was not seeking to establish a US military presence.

"Our commitments are to Afghanistan in that agreement. This is not an agreement with the neighboring countries, as you know the provisions in the partnership agree that the United States will not have permanent bases in Afghanistan and similarly that we will not launch offensive action against other states from Afghan soil," Crocker said.

Crocker made the comments just hours after the pact was signed in Kabul by the Presidents of both nations.

US President Barack Obama made a seven-hour visit to Afghanistan overnight for the occasion.

In Obama's speech to US soldiers at Afghanistan's Bagram military base, he noted that it was from that base exactly one year ago that the operation to kill former al-Qaeda leader Osama bin Laden was launched.

Speculation about whether the US will have permanent bases in Afghanistan after the US-led Nato combat mission ends in 2014 has raged for more than a year.

US officials, including Secretary of State Hillary Clinton, have repeated that America does not want this. However, among Afghan officials, the doubt remains after Afghanistan's National Security Adviser Rangin Dadfar Spanta told parliamentarians that the question of US permanent military bases will be revisited one year from the signing of the strategic agreement.

The long-term agreement does not specify what level of military assistance the US will provide after 2014, but Crocker did not rule out a combat role.

"I would expect that states in the region would recognise that we have a long term commitment to Afghanistan and there is language in that agreement that states that in the event of internal or external threats to Afghanistan our two countries will consult on the appropriate response," he said.

He emphasized that the agreement will not repeat the mistake of the 1990s, when the US withdrew, leaving Afghanistan to slide into civil war.

"We are not repeating the mistake of the early 1990s," Crocker said.

"With full respect for Afghan sovereignty, with full respect for the Lisbon commitments, we will have the Afghan Security forces in full control of this country by the end 2014. We have agreed that we are long term partners through 2024 with a provision of a extension of that agreement beyond that time."