By Pam O'Toole Eurasia analyst

President Khatami of Iran's visit to Afghanistan is one that would have been unthinkable only a few years ago.

Although neighbours, relations between Tehran and Kabul have been icy in recent years.

Iran was an avowed enemy of the Taleban, alleging that the movement brought Islam into disrepute.

Nearly 1.5m Afghan refugees remain in Iran

But in his visit to the Afghan capital Kabul, Iranian President Mohammad Khatami underlined his solidarity with the new regime in Afghanistan.

Old friends

Relations between Tehran and Kabul reached an all time low in 1998.

Then, Iran massed hundreds of thousands of troops along its border with Afghanistan in response to the killing of group of Iranian diplomats by the Taleban.

But the collapse of the Taleban last year brought about a transformation.

Iran became a major ally of the new Afghanistan, assisting in international negotiations to set up an Afghan interim administration and pledging more than $500 million worth of reconstruction aid.

It's been building roads in Western Afghanistan and is continuing to play host - albeit reluctantly - to around one and a half million Afghan refugees.

Sensitive issues

But some underlying tensions remain.

The Iranian President used his visit to again deny American allegations that elements within the Iranian establishment have been attempting to undermine Hamid Karzai's transitional administration in Kabul .

He also emphasised Tehran's part in the international fight against terror.

But Mr Khatami will also be driving home some of Iran's continuing concerns.

These include drug trafficking from Afghanistan, which has caused lawlessness in Iran's border areas.

Iran is helping with reconstruction

Thousands of Iranian security officials have been killed in shoot-outs with traffickers over recent decades.

And then there's the tricky issue of Afghan refugees and migrants.

Tehran recently extended a deadline for undocumented Afghans to leave its territory, but the threat of expulsion still hangs over large numbers of Afghans there.

And most of all, there's the issue of Kabul's friendship with America.

Tehran will be seeking assurances that American forces will not be allowed to stay in Afghanistan in the long-term.