KIEV, December 29 (RIA Novosti) - Ukraine's election commission said Friday it had completed the verification of signatures under an initiative to hold a referendum on NATO accession, and would send it to the president for approval.

The opposition Social Democratic Party collected the signatures in line with Western-leaning President Viktor Yushchenko's efforts to forge closer ties with the alliance, which has encountered opposition from the Russian-speaking population and strained relations with Russia.

The party proposed bringing two issues up for public debate - NATO membership and integration into the post-Soviet Single Economic Space (SES), which presently comprises Russia, Belarus and Kazakhstan.

Central Election Commission Chairman Yaroslav Davydovych said 4,656,182 signatures had been collected and 224,509 of them found invalid.

The national unity pact signed by the core political forces in the ex-Soviet state in August to end their rift stipulates that a decision on NATO should be made following a referendum.

Pro-Moscow Prime Minister Viktor Yanukovych, appointed in August, has been cautious about rapprochement with NATO, and the idea is also unpopular in the country's mainly Russian-speaking eastern and southern regions.

Opinion surveys show that more than 50% of Ukrainian nationals do not approve of joining the former Soviet Union's Cold War foe.

Mass anti-NATO protests rocked Ukraine's Crimean autonomous region in late May-early June after a U.S. cargo ship delivered military equipment to a local port ahead of a NATO exercise. The cargo was later removed following the protests.