The sentence is an example of dolaylı anlatım(reported speech). "Beklediklerini" of course has more than one suffix but what you're asking is probably the last one. We can say that the suffix "-i" here has the function of "that" in reported speech. Experts say that European leaders are expecting a consistent plan from Spain. Uzmanlar, Avrupalı liderlerin İspanya'dan tutarlı bir plan beklediklerini söylüyor He said that he didn't want to go to the party. Partiye gitmek istemediğini söyledi. Parayı çaldığını itiraf etti. He confessed that he stole the money.

It is not -ini suffix, it is -i suffix. It is used to change a verb into the object of the sentence. Beklediklerini= the things that they expect. Uzmanlar: ''İspanya'dan tutarlı bir plan bekliyoruz.'' Uzmanlar İspanya'dan tutarlı bir plan beklediklerini söylüyor. What a difficult question! I know someone can answer you better.:)

'Bekledikleri' as an adjective means 'that/which they await' As in: 'bekledikleri tren' = 'the train which they await' 'bekledikleri cevap' = 'the answer that they expect' As a noun, it means (in this case): 'the fact that they await' (or more literally 'the act of awaiting, by them') 'Bekledikleri belli' = 'it is obvious (the fact) that they await' 'plan beklediklerini söylediler' = 'they said that they await a plan' The -(n)i affix which is added, is due to the fact that here it is used as a direct object in the sentence, as is done with any other (defined) direct object. (As Gul pointed out earlier)

in -possessive İn-i accusative "kitabını" gibi..

Perhaps it would help you to know that often when a word has more than one suffix, an "n" must be used to separate those suffixes. For example, "on his table" would be... masa+sı+n+da... table + possessive + n (separator needed because "table" already had the possessive suffix) + on. I hope this has helped.