The decision to bar 47 volunteers from the U.S. government-run program from the former Soviet state comes amid fears energy-rich Turkmenistan is reneging on commitments to open up after years of isolation under an eccentric autocrat.
"We had the paperwork in place, and they were approved to come, but the day before they were due to leave the U.S., we received a diplomatic note from the embassy saying that they would be invited next year, but not for this year," Leal said by telephone from the Turkmen capital, Ashgabat.
Leal said it was unclear what provoked the decision, but that his organization is waiting to meet with government officials for an explanation on the matter.
The Peace Corps, whose operations in Turkmenistan are devoted to teaching English and health education, is often viewed with suspicion by governments in former Soviet states.
In 2002, Russia expelled the organization and accused some of its volunteers of spying.
The next scheduled group of Peace Corps volunteers is not slated to travel to Turkmenistan until late next year, which Leal said could hamper the organization's operations.
"It is going to have a big effect. Many of the volunteers are completing their service here, so in late December, we will be about half what we currently have," Leal said. He said the group's numbers would drop to about 35 volunteers, as opposed to the usual 70 or 80.
The Peace Corps has sent around 700 volunteers to serve in Turkmenistan since starting operations there in the early 1990s.
Turkmenistan's leadership has made tentative moves to open up the country since the December 2006 death of Saparmurat Niyazov, the autocract who had ruled since before the 1991 Soviet collapse.
His successor, President Gurbanguli Berdymukhamedov, has repealed some of Niyazov's most idiosyncratic policies, including banning opera and the circus for being insufficiently Turkmen. In education, Berdymukhamedov's government has increased basic education to 10 years from to nine years, and higher education has been extended from two years to five.
He has also increased contacts with the West, which is eager for access to Turkenmnistan's natural gas riches.
But fears are mounting that the government is reverting to Niyazov's draconian style of rule.
Last week, the United States criticized efforts by Turkmenistan to prevent students from traveling to U.S.-linked universities.
Over the past few months, Turkmenistan has stopped hundreds of students from leaving the country to take up courses at the American University of Central Asia, in Kyrgyzstan, and the American University in Bulgaria.
U.S. criticism of Turkmen government policy came just weeks after a high-profile meeting in the United States between Berdymukhamedov and U.S. Secretary of State Hillary Rodham Clinton.
Turkmenistan has long been subject over intense rivalry between the West and Russia for access to its vast natural gas reserves, which the government estimates may total more than 700 trillion cubic feet (20 trillion cubic meters).