The most senior American diplomat for Asia says the United States remains a 'steady and trusted' partner of the Philippines. But the US is concerned about recent controversial statements made by President Rodrigo Duterte.

The United States hears Philippine President Rodrigo Duterte. That much is clear now as it's sent its top diplomat for Asia, Daniel Russel, to Manila to clarify where ties between the Philippines and the U.S. stand. Russel met with Philippine Foreign Affairs Secretary Perfecto Yasay on Monday, where he - and U.S. Secretary of State John Kerry over the phone - reaffirmed the United States' commitment to the Philippines.

"For our part, the United States remains steady, and I hope trusted partner, strong ally. We stand ready to honour our commitments. We stand by international law and we stand by the Philippines," said Daniel Russel.

But Russel did express concern about Duterte's anti-American rhetoric, saying his sometimes hurtful, sometimes confusing statements are causing anxiety not only within his government and other governments, but also among the business community, as well as in the Filipino expat community in the United States. But he did acknowledge that Duterte himself had already walked back remarks about separating from the U.S. Duterte says what he meant by separating from the U.S. was a foreign policy that does not take into consideration the United States' interests. He said it was impossible to sever ties with the U.S. And so Russel says that if that was indeed what Duterte meant, then there is nothing to change in ties between the Philippines and the U.S. In fact, he says, the U.S. has always let the Philippines decide on its own. And even its improving ties with China, Russel says, is welcome development for the U.S.

"We support direct dialogue, negotiations between the Philippines and China, as long as they take place on terms that is acceptable to the Philippines. As long as they are consistent with international law. So it's a mistake to think that improved relations between Manila and Beijing somehow come at the expense of the United States," said Daniel Russel.

Now Russell also expressed his government's support for Duterte's campaign against illegal drugs, saying the U.S. has been helping the Philippines in that regard, but he also reiterated his government's concern about alleged drug-related killings, now in the thousands.