By Dave Graham and Sofia Menchu

GUATEMALA CITY (Reuters) - The United States should provide billions of dollars to help Central American nations curb the flow of illegal migrants, Guatemalan President Otto Perez said, and his government warns the problem will get worse if Washington fails to help.

Fleeing violence, trying to reach relatives already in the United States or seeking jobs, record numbers of child migrants from Honduras, Guatemala and El Salvador have been stopped at the southern U.S. border this year, causing widespread alarm.

Last month, the three countries pitched Washington an ambitious development plan to confront the issue.

They want to pump about $10 billion into the region to create jobs and lift living standards, with the bulk of funding coming from the United States, Perez told Reuters.

He hopes the plan could come up with about $2 billion a year from 2015 to 2019, a sum he equated to roughly 10 percent of annual U.S. spending on border security and immigration enforcement.

"Now we understand it's not simply a question of the United States saying: 'Right, here's $2 billion a year for five years' for example - the governments of the three countries have to play their part too," the conservative Perez, who took power in early 2012, said in an interview late on Monday.

The package would boost infrastructure and provide more jobs in all three countries, especially in areas that send large numbers of migrants to the United States, he added.

The three Central American governments are urging the United States to shoulder the lion's share of the costs, arguing that U.S. demand for illegal narcotics has fueled violence among drug gangs across much of the impoverished region.

"The United States has to support this, it has no other option," Guatemala's foreign minister, Carlos Morales, told Reuters. "If they don't support it, the crisis will kick off again, you can count on it."

Perez said he hoped the United States would put up about 60 percent of funding. "But we'll have to discuss it calmly and see what each individual country can do, and what can be achieved by common consent."

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During meetings in New York in September, U.S. Secretary of State John Kerry told Central American officials he hoped Congress could approve about $300 million in funding, Morales said, noting the sum was "nothing" given the scale of the problem.

Central American leaders are due to meet Vice President Joe Biden on Nov. 12 in Washington to sound out U.S. support for their plan, Morales added.

IMPROVE INFRASTRUCTURE

The initiative contains proposals to overhaul energy supply, roads, airports, and other key infrastructure in the region, alongside various other measures.

Known as the "Plan of the Alliance for Prosperity in the Northern Triangle", it is being seen by some as a more limited version of "Plan Colombia', under which the U.S. government sent billions of dollars in aid to help Colombia fight drug traffickers and left-wing guerrillas.

Multilateral loans and private sector funds are among the options being considered, and Perez said Guatemala has held talks with the Inter-American Development Bank and the World Bank on possible funding proposals, including loans.

The flood of children heading to the United States from Central America this year stretched U.S. border facilities to their limits and images of youngsters packed into holding centers near the border caused a political storm.

A concerted drive to dissuade them finally reduced the flow, but by the end of September, U.S. officials had stopped 67,339 unaccompanied minors from Guatemala, Honduras, El Salvador and Mexico on the southwest border over the previous year.

Since 2009, the number of children arriving from Guatemala, Honduras and El Salvador has risen nearly 16-fold, and the three nations had the most caught in 2014. Five years ago, Mexico accounted for more than 80 percent of the combined total.

There are far fewer migrants from other Central American countries like Nicaragua, Costa Rica and Panama.

Alongside financial backing for the development plan, Guatemala is pushing Washington to grant more concessions to migrants in return for its own efforts to reduce the exodus.

These include more visas for temporary workers and urging U.S. President Barack Obama to use his executive powers to improve rights of certain illegal immigrants with good records in the United States - such as those with U.S.-born children - if Congress fails to pass a stalled immigration reform.

(Reporting by Dave Graham; Editing by Kieran Murray)