Hezb-i-Islami, one of the main rebel groups in Afghanistan, offers to fill peacemaker role but critics say group has little influence.

One of the main insurgent groups fighting the Afghan government and its Nato backers said today that it was ready to make peace and act as a bridge to the Taliban if the US began pulling out troops next year, as planned.

A spokesman for a delegation from the Hezb-i-Islami, which has been holding talks in Kabul this week with President Hamid Karzai, said the group's initiative was prompted by Barack Obama's declaration that American forces would begin to be drawn down.

"There is a formula: 'no enemy is an enemy forever, no friend is a friend forever,' " Mohammad Daoud Abedi told Reuters. "If that's what the international community with the leadership of the United States of America is planning – to leave – we had better make the situation honourable enough for them to leave with honour."

The talks between Karzai and Hezb-i-Islami appear to be at an early stage, and it is unclear how ready the Afghan president is to strike a deal with the group's leader, Gulbuddin Hekmatyar, a ferocious warlord who was responsible for reducing much of Kabul to rubble with his artillery in the 1990s.

It is also unclear how much influence Hezb-i-Islami would have on the Taliban. The two groups have had a volatile relationship and clashed this month in northern Afghanistan.

"We have only one common situation with the Taliban, which is the withdrawal of the foreign forces and the freeing of the country from the occupation," Abedi said. "The rest of the things, they have their opinion and we have ours. We believe in free and fair elections, and the Taliban have a different idea."

He added, however, that his group could be "a bridge between [the] two sides".

The Hezb-i-Islami delegation presented a 15-point peace plan to Karzai, which included a demand for foreign forces to begin withdrawing in July this year, but Abedi signalled that the group could be flexible on dates if Washington demonstrated good faith in its intentions.

"First of all, this is not written in stone and it's not the verse of the Qur'an, not to be changed. This is a starting point," Abedi said.

"If we agree on this departure date: OK, the US will leave. Give us a timeframe. They have said 18 months.

"So if we come to an agreement, and preparations are actually taking place ... that is considered a positive step.

"That is considered that the US really means withdrawal. Because right now, there is a problem of trust between both sides."

The peace talks with Hezb-i-Islami will help provide some momentum for Karzai's planned loya jirga – grand peace council – next month, but some observers question the real substance of the talks.

Michael Semple, a former UN and EU representative in Afghanistan, said: "This is really politicking among those people already on board with the process. This has nothing to do with ending the insurgency."

Semple, now at the Carr Centre for Human Rights Policy at Harvard University ,said: "This is a long way from pulling Gulbuddin in. He has had feelers out for quite a while.

"But in reality, Gulbuddin doesn't have much to offer, and there are heavy costs for Karzai to bring him in. He is toxic [politically] and very demanding."

US embassy spokeswoman Caitlin Hayden said that American officials had no plans to meet Gulbuddin's group.