WASHINGTON - US President Barack Obama on Saturday stepped up pressure on Libyan leader Muammar Gaddafi, saying that he should leave now.

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In a telephone call to German Chancellor Angela Merkel on the situation in Libya, Obama said the Libyan leader "has lost the legitimacy to rule and needs to do what is right for his country by leaving now", the White House said in a statement.

They discussed "appropriate and effective ways" for the international community to respond, the statement said.

Obama ordered on Friday to freeze assets of the Libyan government, Gaddafi and his family following the suspension of US embassy operations in Tripoli earlier in the day.

Gaddafi has said that he would not leave his country but rather die "as a martyr".