(Adds Guatemalan legal challenge)
By Sofia Menchu
GUATEMALA CITY, July 11 (Reuters) - Guatemalan President Jimmy Morales will travel to Washington next week to discuss migration, while five former senior officials went to court to block an agreement Morales may sign declaring the Central American country a safe destination for asylum seekers.
The appeal to Guatemala's Constitutional Court, made public on Thursday, was signed by four former Guatemalan foreign ministers and a high-ranking diplomat. It seeks an injunction against any agreement with the United States that would declare Guatemala a "safe third country" for asylum seekers.
The legal argument says such an agreement would be a "very grave" move that would "obviously be harmful" to Guatemala and its inhabitants, adding that its authors' deep foreign affairs and diplomatic experience gives their assessment added credibility.
The court could take weeks to reach its decision.
Morales will visit President Donald Trump at the White House on Monday, and "meet with U.S. Government officials to address security, migration and economic issues," the Guatemalan government said in a statement on Twitter on Thursday.
A U.S. government source briefed on the matter and a Guatemalan presidential source, speaking on condition of anonymity, both said Morales may sign a "safe third country agreement" with Trump on Monday. Both emphasized that some details were still being finalized, after weeks of intense negotiation.
White House officials did not immediately respond to requests for comment.
Trump said on June 26 that the United States and Guatemala were close to reaching such an asylum agreement, as part of efforts to curb U.S.-bound migration from Central America.
Declaring Guatemala a safe third country would require changes to its immigration laws.
Under such an agreement, Guatemala would be obliged to process asylum claims from migrants who entered its territory en route to the United States. Migrants from Honduras and El Salvador heading to the U.S.-Mexican border overland usually cross into Mexico via Guatemala.
The poor country of 17 million people has its own problems with gang violence and a weak justice system. Large numbers of Guatemalans have sought refuge in the United States, leading civil rights groups to warn it is not a safe destination for asylum seekers.
Guatemala has one of the highest homicide rates in Latin America, according to United Nations data.
Giovanni Filippo Bassu, the regional representative for the UN High Commission for Refugees (UNHCR) said in June that Guatemala had a long way to go before it would be safe for asylum seekers fleeing neighboring countries.
"This agreement would be an egregious violation of law and common decency," Refugees International President Eric Schwartz said on Thursday. Guatemala's lack of security could trap migrants escaping violence in El Salvador and Honduras in a situation similar to the one they are trying to flee, he said.
Guatemalans claiming asylum in the United States outnumbered those from Honduras and El Salvador in 2017, according to data available from the U.S. Department of Homeland Security.
The apprehension by U.S. authorities of Central American migrants, including large numbers of families and asylum seekers, reached a more than decade high in May. Trump has applied increasing pressure on Mexico and Central America to stem the flows.
Cracking down on immigration has been a long-standing priority for Trump. In June, he moved to cut U.S. aid to Guatemala, El Salvador and Honduras over the rise in migration numbers, but added that Guatemala "is much different than it was under past administrations."
The only other safe third country agreement currently maintained by the United States was negotiated with Canada in 2002.
(Reporting by Sofia Menchu; Additional reporting by David Shepardson, Lizbeth Diaz, Rebekah F Ward and Roberta Rampton; Writing by Rebekah F Ward; editing by Frank Jack Daniel, Rosalba O'Brien and Lisa Shumaker)