CARACAS (AFP) - Venezuelan President Nicolas Maduro urged United States president Barack Obama to "accept the challenge" and hold direct talks, a surprise overture made on Friday after days of accusing Washington of plotting his overthrow.

The announcement came after nearly three weeks of often violent anti-government protests in Caracas and other major cities, the biggest test to Mr Maduro since he succeeded leftist icon Hugo Chavez last year.

In Washington, Secretary of State John Kerry chastised Caracas for its crackdown, but nothing about direct talks.

"I am watching with increasing concern the situation in Venezuela," the top US diplomat said in a statement, pointing to the government's use of force against peaceful protesters, the jailing of protesters and a tightening of media restrictions.

"This is not how democracies behave," he said.

Venezuela's relations with the United States, long strained under Mr Chavez, have worsened under Mr Maduro, who has never spoken directly to his US counterpart.

Mr Maduro, who was narrowly elected last year, said: "I call a dialogue with you, President Obama... between the patriotic and revolutionary Venezuela and the United States and its government." His government claims that Venezuelan opposition leaders are in Washington's pay.