The UN Latin American and Caribbean Group has endorsed Panama to take its non-permanent seat on the Security Council, diplomats said.
Panama should now succeed Argentina on the council
Panama was unanimously backed after Guatemala and Venezuela agreed to withdraw following nearly 50 rounds of voting that failed to separate them.
Panama should now be formally elected by the General Assembly on Tuesday.
The US had opposed Venezuela's candidacy because of its relationship with President Hugo Chavez.
"It was unanimous," Argentina's Ambassador Cesar Mayoral said after the UN Latin American and Caribbean Group met behind closed doors on Friday.
Five permanent members
Ten elected to serve two-year terms
Each year five elected members change, within regional blocs
Arab state always represented in Africa or Asia bloc
Panama should now succeed Argentina on the 15-member Security Council in January.
The UN General Assembly held 47 rounds to choose between Guatemala and Venezuela.
Guatemala gathered more support in nearly all the rounds, but neither side was able to achieve the two-thirds majority needed in the 192-member General Assembly.
Diplomats said that Mr Chavez's now infamous speech to the UN General Assembly in September, during which he compared US President George W Bush to the devil, had damaged his country's standing.
CURRENT ELECTED MEMBERS
(Replaced from 2007 by country in brackets)
Tanzania (South Africa)
*To be formalised
Five of the 15 UN Security Council seats are held permanently by China, the US, Russia, the UK and France.
The others are held by regional blocs from Africa, Latin America, Asia, Western Europe and Eastern Europe.
Other regional seats, which are rotated every two years, went to Indonesia, South Africa, Italy and Belgium in the first round of voting last month.