WASHINGTON: Calling China the "worst abuser" and "currency manipulator", Republican presidential candidate Donald Trump warned that if elected, he will identify all countries violating trade agreements and take serious actions against them.The 70-year-old real estate tycoon-turned-politician said he will instruct the US trade representative to bring trade cases against China, which is also building a "massive military fortress" in the strategic South China Sea.Trump said he would direct the Secretary of Commerce to identify every violation of trade agreements that a foreign country is currently using to harm American workers."China is the worst abuser," Trump said."They have no respect for our country. They have no respect for our leadership. And we don't blame them, we don't blame them. We want to put ourselves in that position very soon. You watch. And they'll like us better than they do now," he said."They don't like us. They're building a massive military fortress in the middle of the South China Sea that they're not allowed to do."They're doing that, and yet, they're ripping us economically. We have tremendous power over China - economic power - tremendous. We don't do anything. They build and build and build, and they didn't get environmental impact statements when they decided to rip up the sea," he told supporters at an election rally in Tampa, Florida."They said - Sunday night, let's build. Monday morning, they were digging. A little different than our country, wouldn't you say? A little different. A little bit different," he alleged."I don't think our politicians even know what's going on. And they will stop or we're going to take in one hell of a lot of money, I'll tell you that. I'm going to instruct the United States trade representative to bring trade cases against China, both in this country and at the World Trade Organisation ( WTO )," Trump said.Trump further said he would instruct his treasury secretary to label China a "currency manipulator," the greatest in the world"."Any country that devalues their currency in order to take unfair advantage of the US and all of its companies who can't compete will face tariffs and taxes to stop the cheating. And when they see that, they will stop the cheating," he said."China's unfair subsidy and its behaviour is prohibited by the terms of its entrance into the WTO, and I intend to enforce our rules. That's all. Very simple," he added."And they know it's coming. They've called a lot of friends of mine. They know it's coming. They say, "What do we do? What do we do?" If China does not stop its illegal activities - remember this. Our trade deficit with China is approximately $505 billion a year," Trump said.