The UN must consider further sanctions against Iran if Tehran does not respond to UN demands over its nuclear program, German Chancellor Angela Merkel said in a newspaper interview.

Merkel told German daily Die Welt the Islamic Republic threatened the whole world and had to be contained.

'I'm emphatically in favor of solving the problem through negotiations, but we also need to be ready to impose further sanctions if Iran does not give ground,' she said.

'It is threatening the security of Israel which for me as German Chancellor will never be negotiable. It threatens the region, Europe and the world. We must prevent that.'

The UN Security Council has passed two sanctions resolutions against Iran for failing to halt uranium enrichment.

Merkel is due to hold a joint press conference with Russian President Vladimir Putin in Wiesbaden later on Monday.

Putin's arrival followed an Interfax news agency report which said Russian special services had been warned of a plot to assassinate Putin when he visits Iran on Monday evening.

The US, the EU, Russia and China -- have offered Tehran a package of economic, civil nuclear and security incentives if it suspends its most sensitive atomic work. Reuters