Relations between Venezuela and the US will not improve even if Barack Obama becomes president, Hugo Chavez, the Venezuelan leader, predicted on Thursday.

A persistent thorn in the side of the US, Chavez told his supporters not to get their hopes up over Obama, the Democratic candidate, as there was little difference between him and his Republican rival, John McCain.

"The two candidates for the US presidency attack us equally, they attack us defending the interests of the empire," Chavez said at a meeting of his socialist party. "Let's not kid ourselves, it is the empire and the empire must fall. That's the only solution - that it comes to an end." Obama has taken a tougher line towards Chavez in recent weeks as he continues to harden his international image in an attempt to broaden his appeal to more conservative voters.

Earlier on in his White House campaign, Obama said he would be prepared to sit down to talk with Chavez. Now he describes the populist Venezuelan leader as an enemy of the US and urges sanctions against him. Accordingly, Chavez - who had previously expressed hopes for better ties post-Bush - has also sharpened his tone against Obama. He said Obama should not expect a "carrot and stick" diplomacy to help the US exert its influence in Latin America.

"A revolution has been unleashed in this land," Chavez said, in words directly addressed to Obama. Relations between the US and Venezuela have been strained since 2002 when the Bush administration welcomed a coup - that failed - against Chavez. Since then, the Venezuelan leader has taken regular verbal potshots at the US, even though the two have important economic ties; Venezuela is one of America's top crude oil suppliers.

Chavez's latest salvo at what he calls "the empire" comes at a time when the Bush administration appears increasingly willing to play the diplomatic card, dropping its previously hawkish foreign policy approach.