The aging craft, heading toward the Strait of Malacca, is an unlikely player in what is fast becoming an international drama.
Chevron has evacuated hundreds of employees from the oil-rich region of Nigeria after a string of attacks on oil pipelines.
Despite street violence on Saturday that officially claimed 13 lives, opposition leader Mir Hussein Mousavi again on Sunday called for the June 12 election results to be annulled.
The incumbent president will be easier to isolate than reformist leader Mr. Mousavi, say some leading Israeli policymakers.
Eyewitnesses say thousands of police and plainclothes militia members filled the streets to prevent rallies.
On Friday, the supreme leader raised the stakes by giving Ahmadinejad full support and insisting that there was no fraud in the election.