Barack Obama''s administration had its first direct contact with Iran Tuesday at a conference on Afghanistan where America and its old foe found common cause on rebuilding the war-torn state.

But, in a sign Tehran and Washington are far from reconciled, Iran warned that the planned US troop surge in Afghanistan would fail to crush the Taliban-led insurgency there.

US Secretary of State Hillary Clinton said top American and Iranian officials met at the international conference in The Hague.

"Our special representative for Afghanistan, Richard Holbrooke, had a brief and cordial exchange with the head of the Iranian delegation," she told reporters.

But Iran''s representative Mohammad Mehdi Akhoundzadeh warned that President Obama''s promised surge of US troops was a mistake.

"The presence of foreign forces has not improved things in the country and it seems that an increase in the number of foreign forces will prove ineffective too," the Iranian deputy foreign minister told the conference.

More than half of the 70,000 foreign soldiers in the unruly central Asian state are Americans.

Obama said last Friday he would send 4,000 more US troops to train Afghan security forces in addition to an extra 17,000 already committed.

Iran has not had diplomatic relations with the US for nearly three decades, and was included in former president George W. Bush''s "axis of evil."