By Jonathan Kent
BBC correspondent in Kuala Lumpur
Malaysia has rejected a proposal that the United States help patrol one of the world's busiest waterways.
There are warnings militants might try to seize boats
America's top military commander in the region said Washington intended to use US forces to counter possible terrorism in the Straits of Malacca.
However, it appears that he failed to consult Malaysia, which along with Indonesia borders the straits.
Malaysia said the US should have sought its consent on what it called an issue of national sovereignty.
The head of the US Pacific Command, Admiral Thomas Fargo, said there was widespread support for the initiative.
He wants to deploy speedboats carrying marines and special forces along the narrow straits.
Reports that Islamic militants may be planning to seize vessels to use as floating bombs have fuelled concerns about the rising number of attacks on ships in the region.
The admiral says he has secured Singapore's backing, but the waterway is largely divided between Malaysia and Indonesia.
Malaysia's Deputy Prime Minister Najib Tun Razak politely but firmly turned the admiral down.
He said that Malaysia had no plans for the present to invite the Americans to join in regional security operations.
He gently warned Washington that the US could not deploy its forces without Malaysia's consent, saying it was an issue of national sovereignty.
The United States has dubbed South East Asia its second front in the war on terror and Malaysia has been a valued ally in that war.
However, the Bush administration is unpopular both in Malaysia and Indonesia, and not just among Muslims.
Analysts say there would be considerable public resistance to US military deployment within either country's borders.