By Jill McGivering BBC News, Sofia

Powell is making his last planned trip to Europe as secretary of state

Mr Powell will hold talks with security organisations, the OSCE and Nato, and attend an EU-US ministerial reunion.

The visit comes amid intense debate in about institutional reform and the transatlantic relationship.

The visit is Mr Powell's last scheduled trip in his post as secretary of state before he is replaced by Condoleezza Rice in January.

'Critical'

For the next few days, Mr Powell will travel from Sofia to Brussels to the Hague, taking part in meetings of these key European institutions and giving US input on their future shape and direction.

This visit comes at a critical point in US relations with Europe.

Since his re-election, President George W Bush has promised to repair the US-European alliance, damaged by disagreement over Iraq.

He has also pledged to respect multinational organisations and work within their framework in his second term.

The last few weeks have been marked by a flurry of transatlantic visits and fresh consultations on central issues like Iraq and the Israeli-Palestinian conflict.

The coordinated diplomatic pressure on Ukraine which helped to avert a crisis is being hailed as early evidence of restored cooperation.

But some critics are sceptical. They say President Bush's pledges are carefully qualified, suggesting the US is still intolerant of lengthy debate and diplomacy.

They say the continuing public split between the US and Europe over tackling Iran's nuclear programme is a better indication of the continuing difference in approach.

Mr Powell was considered the Bush administration's strongest champion of multilateralism.