Senior officials from European institutions at Sunday's ceremony will include Justice Minister Luc Frieden representing the EU's Luxembourg presidency, and EU External Relations Commissioner Benita Ferrero-Waldner.

Ukraine's parliament set a date for Yushchenko's long-delayed investiture Thursday, after the supreme court cleared the way for the pro-Western reformer to assume power in the ex-Soviet nation following months of political turmoil.

EU foreign affairs chief Javier Solana, who played a key role mediating between the camps of Yushchenko and his Moscow-backed rival Viktor Yanukovich, was at first billed to attend Sunday's inauguration event.

But he has a prior engagement and will instead travel to Kiev on Friday for a day of high-level talks, his office said.

The Spanish official is due to meet Yushchenko as well as outgoing president Leonid Kuchma and the speaker of parliament, Volodymyr Litvin, sources said.

The head of the North Atlantic Treaty Organisation said he had confidence that Yushchenko could pursue "far-reaching political and economic reforms".

"Be assured that NATO stands ready to support your government's efforts to implement the ambitious common goals and principles that underpin our deepening relationship," de Hoop Scheffer said in a letter of congratulations.

Yushchenko's inauguration will cap months of uncertainty that convulsed Ukraine and sparked Cold War-like exchanges between Russia and the West following a disputed election in the country in November.

Both the European Union and NATO, however, have said it is premature to talk of Ukraine's entry into the organisations.