British Prime Minister Theresa May has said she was "deeply disappointed" at the unjustified decision by the US to apply tariffs to European Union (EU) steel and aluminium imports.Her comments on Friday came a day after US President Donald Trump announced the decision to levy tariff amid waves of criticism, Xinhua news agency reported.May said in a statement that the US, the EU and Britain are close allies and have always promoted values of open and fair trade across the world."Our steel and aluminium industries are hugely important to the UK, but they also contribute to US industry including in defence projects which bolster US national security," she said."The EU and UK should be permanently exempted from tariffs and we will continue to work together to protect and safeguard our workers and industries," the Prime Minister added.The tariffs of 25 per cent on steel products and 10 per cent on aluminium, which affect the EU, Canada and Mexico, came into effect on Friday.