The theme of this year's Suffering Church Sunday, 'Be on Your Guard', reflects Barnabas Fund's growing concerns over the freedom of Christians in the West.
It described as "worrying" the case this week of Eunice and Owen Johns to decide whether their Christian beliefs make them unfit to foster children.
Barnabas Fund is asking churches in the UK to remember Christians in other parts of the world who are suffering for their faith but also equip themselves to be ready for persecution too.
Dr Patrick Sookhdeo, International Director of Barnabas Fund, said: "It is understandable in the West – a bastion of freedom and tolerance – Christians tend to think that persecution is something that happens only to believers in far-flung places.
"But it is becoming increasingly apparent that we too need to steel ourselves for suffering if we are going to make a stand for Christ."
Ashley Samelson, International Programmes Director for the Becket Fund for Religious Liberty, expressed concern over the case of the Johns.
"The outright violence and injustice endured by our brothers and sisters throughout the non-Western world, like the atrocious hostage siege in Iraq on Sunday, is what we tend to consider persecution," she said.
"But more insidious threats are creeping into Western society – and we need to be prepared."
Samelson went on to say that full religious liberty, including the freedom to choose one's faith, was "under attack". She said it was being "publicly undermined" by world leaders on the international stage, including US President Barack Obama, US Secretary of State Hillary Clinton and British Home Secretary Theresa May, who have adopted the term "freedom of worship" instead of "freedom of religion".
She said: "Any person of faith knows that religious exercise is about a lot more than freedom of worship. It's about the right to dress according to one's religious dictates, to preach openly, to evangelise, to engage in the public square."
Barnabas Fund is offering churches free resources for its Suffering Church Sunday, including a DVD, sermon outline, Bible study and prayer/response cards.
Visit: www.barnabasfund.org