Britain has been enjoying faster growth than many other developed economies but dark clouds are gathering on the horizon.

In prepared remarks ahead of a speech Thursday, finance minister George Osborne warned the U.K. was facing a "dangerous cocktail" of risks around the world, and must therefore stick to painful reforms and spending cuts.

Global growth was sluggish last year, Osborne noted, and events this week could spell more trouble.

"Already we've had worrying news about stock market falls around the world, the slowdown in China, deep problems in Brazil and in Russia," Osborne said.

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After five years of austerity, there are growing calls across the political spectrum to slow down further cuts. Osborne said his government had to stay the course.

"Though the year is only seven days old, already we hear their predictable calls for billions of pounds more debt-fueled public spending," said Osborne.

He also noted that steep falls in oil prices might be good for consumers, but not for the country's oil and gas sector, nor for the banks and others who have lent money to the industry. Rising tension in the Middle East was also a worry.

"The political developments in the Middle East, with Saudi Arabia and Iran, concern us all," said Osborne.