By Nick Childs
BBC World Affairs correspondent
A Chinese official has issued a new warning over US arms sales to Taiwan.
The US sells missiles to Taiwan under a special agreement
In a broad policy document on arms control, China also says it is against any government providing Taiwan with missile defences.
The statements comes ahead of Chinese President Hu Jintao's visit to Washington next week, for talks with US President George W Bush.
The summit will be a very significant meeting, testing the diplomatic waters between the two nations.
On Thursday, a Chinese foreign ministry spokesman again called on the US to stop selling advanced weapons to Taiwan.
Beijing has also come out with a broad policy document that looks like a direct answer to the recent drumbeat of warnings from Washington over China's military modernisation plans.
It insists Beijing is pursuing what it calls "moderate" increases in defence spending, reiterates a policy of no-first-use of nuclear weapons, and says essentially that the outside world has nothing to fear - China will never seek hegemony, as it puts it.
But here, too, there is a warning over Taiwan - that governments, again by implication the US, should not include it in any missile defence plans.
Washington has justified its offer to upgrade Taiwan's defences, in part because of what it sees as a threatening build-up of missile forces on China's side of the Taiwan Straits.
And the Pentagon's latest report on China's military modernisation described it not only as a potential threat to Taiwan, but also as a threat to other major powers in the region, and the US presence there as well.
The military and strategic tensions between the two are, of course, just one element in what is a hugely complex, developing, and potentially antagonistic relationship between an emerging giant and the world's only current superpower - one which each side appears still to be grappling to contend with.