Nato has hinted to Ukraine that its hopes of joining the transatlantic alliance could be fulfilled.
Nato's Secretary General Jaap de Hoop Scheffer said Nato was open to democracies that met the membership criteria. But he set no target date.
Ukraine's new liberal president, Viktor Yushchenko, met Nato leaders including US President George W Bush at a summit in Brussels on Tuesday.
He told them he would like Ukraine to be integrated into the EU and Nato.
Earlier Mr Bush, who had a brief face-to-face meeting with Mr Yushchenko, called upon his European allies to welcome Ukraine "into the Euro-Atlantic" family.
The BBC's Jonathan Marcus says Mr de Hoop Scheffer was at pains to stress at the meeting with Mr Yushchenko that support for Ukraine should not become a contest between what he described as East and West.
On the practical side, Nato has promised to finance a massive project to destroy tonnes of surplus weaponry in Ukraine.
For his part, Mr Yushchenko said his country was interested in taking part in peacekeeping operations.
However, the pullout of Ukrainian troops from Iraq, where the country deployed the fourth-largest contingent in the US-led coalition, was one of the main promises Mr Yushchenko made during his election campaign.
Mr Yushchenko was sworn in last month, after a bitterly fought marathon presidential race against a Moscow-backed rival, Viktor Yanukovych.
The poll exposed divisions between the pro-Russian east of the country and the west, which looks more towards the European Union.
Mr Yushchenko has to manage an uneasy balancing act between the West and Moscow, correspondents say. He reiterated during his Brussels visit that he viewed Russia as "a strategic partner".
On the eve of the Brussels meeting, he held talks with Russian Foreign Minister Sergei Lavrov, on his first visit to Kiev since the "orange revolution" ousted the old government.