If NASA and ESA fail to reach a compromise with Rosaviacosmos this flight, Tito will be launched to ISS on April 30 "regardless of the position of foreign partners," Koptev warned in the strongest remarks he has made on the issue ever since Russia's ISS partners publicly voiced criticism for inclusion of the U.S. millionaire into the three-strong visiting crew in January.

Koptev said that "it is of principal" importance for his agency to launch Tito, along with Russian cosmonaut Yuri Baturin and his Kazakh counterpart Talgat Musabayev, to ISS as the flight of this U.S. citizen will generate a "formidable amount" of cash for Russia's cash-strapped space industry. Tito is to pay a total of $20 million for his visit to ISS.

Koptev's statement came as teams of Rosaviacosmos and NASA officials were still trying in Moscow to negotiate a compromise on the issue of Tito's flight, as well as agree upon a draft document that would regulate selection and certification of both professional and commercial ISS crew members, a senior official of the Russian space agency told SPACE.com

Teams led by deputy director of Rosaviacosmos Valery Alaverdov and NASA's ISS program director Michael Hawes discussed Tito and the draft document from March 13 to 15, but to no avail, said the official, who asked not to be named.

"Unfortunately, our positions on the issue of Tito and space tourism continue not to coincide," the official said. The two sides have not even agreed to fix an exact date for yet another meeting of the so-called Bilateral Crew Operations Panel, he said.

Both the official and Koptev previously told Space News that those agreements that ISS partners have signed, do not oblige Russia to seek permission when selecting and launching visiting crews. These agreements only require that Russia notify its ISS partners that visiting crew members will be launched and when, which it already did in November, according to the Rosaviacosmos official, who asked not to be named.

A NASA official, familiar with details of the Moscow negotiations, confirmed in a phone interview on March 15 that the two sides have failed to reach a rapprochement. "It is true," the official said when asked whether the talks failed. The official, who asked not to be named, told SPACE.com that "we, however, hope to continue negotiations and reach an agreeable solution."

NASA officials maintain that Tito, 60, should not be launched on April 30 since the station is incomplete and his presence may hinder the crew's construction efforts.

Meanwhile, Tito has resumed his training at the Gagarin Cosmonaut Training Center in Star City, an official at this facility said in a phone interview on March 15.

According to the official, who asked not to be named, Tito is taking the so-called survival course which helps crew members to survive if their Soyuz TM capsule lands in a desolated area and rescuers are unable to immediately locate them, the official said.

Having completed this course, Tito will have to fly to Johnson Space Center along with Baturin and Musabayev for more training. The trio will be examined by U.S. doctors before undergoing this training. Rosaviacosmos hopes that U.S. medics will not find the 60-year-old Tito unfit, the Russian space official said. He noted the U.S. doctors' diagnosis will not be legally binding and that Russian doctors have already found Tito fit to fly.

The official didn't rule out, however, that Tito's flight will be rescheduled if the wealthy investment manager bows to NASA's pressure and agrees to such a delay.

Earlier this month, Rosaviacosmos chief Koptev told Space News that NASA is trying to talk Tito into snubbing the April 30 flight in exchange for a guaranteed visit to ISS in October.

"Apparently, if they [Tito and NASA] agree upon such a postponement, they will have to ask for our consent and we will most likely agree," the Rosaviacosmos official, who asked not to be named, said.

ESA contacted Rosaviacosmos earlier this year, suggesting that its veteran astronaut Thomas Reiter be launched to ISS on April 30 instead of Tito, the official said.

"It won't be a problem to train Reiter for such a flight, as he has already been to Mir, but problems will arise" with providing him with a spacesuit, as well as tailoring the Soyuz TM seat, already set up for Tito, for the ESA astronaut, the Russian space official said.