Colombia tightens security ahead of U.S. President George W. Bush's visit. Bush is expected to arrive on Sunday to Colombia, Washington's closest ally in Latin America. Colombia is engaged in a 4-decades-old war and officials have said that the largest rebel group, the FARC, was planning an attack. Colombia's capital of Bogota has been locked down in preparation for U.S. President George W. Bush's seven-hour visit to the Andean nation on Sunday (March 11). Television images from Saturday (March 10), showed tanks and soldiers patrolling the streets and searching cars at numerous checkpoints throughout the city. According to authorities in the Colombian capital, some 22,000 members of the national guard have been deployed in and around the city in a strict land and air security operation designed to ensure Bush's safety. Members from all branches of the Colombian National Guard are being aided by the expertise and high-tech equipment of the U.S. Secret Service to protect the city of 7 million against possible terror attacks by leftist rebel groups. At a news conference yesterday, Colombian President Alvaro Uribe, made it clear that he appreciated the U.S. government's help in the drug war. "We are receiving the head of a friendly country, and we are receiving a president who is a friend, whose complete intention has been to help Colombia in our process to overcome terrorism and drugs trafficking," Uribe said from Bogota. Colombia continues to suffer from the longest armed conflict in the hemisphere, a nearly four-decade-long civil war driven by the drug trade. The leftist rebel group the FARC and the paramilitary organisation Army of National Liberation (ELN) are considered to be terrorist organisations by the U.S, who has given the Colombian government nearly 5 billion USD in aide since starting the ant-drug campaign known as Plan Colombia in 2000. The visit is Bush's second to Colombian - he went to Cartagena in 2004 - and just the first visit of a U.S. president to Bogota since former president Ronald Reagan went in 1982. Bush's arrival comes only days after police intelligence revealed plans by the Revolutionary Armed Forces of Colombia (FARC) to attack the city with explosives and spoil the U.S. president's visit to Bogota. As has happened in Brazil and Uruguay - the first two stops on Bush's Latin American tour - worker's unions, student's organisations, and leftist political parties opposed to Bush will be on hand to voice their discontent. Beyond the war on drugs, Bush and Uribe are expected to discuss moving forward with free trade agreements and the manufacturing of alternative energy sources like ethanol. Meanwhile, snipers armed with high precision rifles are going to be located on the buildings surrounding the presidential palace and military groups in the towns surrounding the city will control the flow in and out of Bogota. Authorities prohibited the carrying of firearms and the sale and consumption of alcoholic beverages. Bush is currently in Uruguay and will move on to Guatemala after his stopover in Colombia.