What does this mean?

It is not a misspelling.

One of the differences between US English and British English is the spelling of SOME words such as materialise finalise scrutinise etc.

In US English they end -ize.

In British English they end -ise.

The broad rule is that the -ize forms are standard in the US, but that -ise ones are now usual in Britain and the Commonwealth in all but formal writing. For example, all British newspapers use the -ise forms; so do most magazines and most non-academic books published in the UK. However, some British publishers insist on the -ize forms (Oxford University Press especially), as do many academic journals and a few other publications (the SF magazine Interzone comes to mind). Most British dictionaries quote both forms, but ?- despite common usage ?- put the -ize form first.

The original form, taken from Greek via Latin, is -ize. That's the justification for continuing to spell words that way (it helps that we say the ending with a z sound). American English standardised on the -ize ending when it was universal. However, French verbs from the same Latin and Greek sources all settled on the s form and this has been a powerful influence on British English. The change by publishers in the UK has happened comparatively recently, only beginning about a century ago (much too recently to influence American spelling), though you can find occasional examples of the -ise form in texts going back to the seventeenth century.

I like the -ise forms myself, in part because being British I was brought up to spell them that way, but also because then I don't have to remember the exceptions. There are some verbs that must be spelled with -ise because the ending is a compound one, part of a larger word, and isn't an example of the suffix. An example is compromise, where the ending is -mise, from Latin missum, something sent or placed. Some other examples spelled -ise are verbs formed from nouns that have the s in the stem, such as advertise or televise.

Not all words vary however. These are the words always spelled in -ise, whatever your local rule about the rest: advertise, advise, apprise, chastise, circumcise, comprise, compromise, demise, despise, devise, disfranchise, enfranchise, enterprise, excise, exercise, improvise, incise, premise, revise, supervise, surmise, surprise, televise.

I know where I got confused
Thank you very much, dear contrex, I know where I got confused.
materialise/ze is used here as a verb, so

means
only if the presumed threat from Iran becomes a fact.