Europe wants a decision in 2010 on an extension to the life of the International Space Station (ISS).
At the moment, no programme for its use nor any funding has been put in place to support the platform beyond 2015.
But the European Space Agency's (Esa) Director General, Jean-Jacques Dordain, told the BBC the uncertainty was undermining best use of the ISS.
He said he was persuaded of its worth, and expressed the desire to keep flying the station until at least 2020.
Only by guaranteeing longevity would more scientists come forward to run experiments on the orbiting laboratory, he argued.
"I am convinced that stopping the station in 2015 would be a mistake because we cannot attract the best scientists if we are telling them today 'you are welcome on the space station but you'd better be quick because in 2015 we close the shop'," he said.
The weightless environment on the station enables scientists to study systems and processes without the bias of gravity. Already it is providing new insights into infectious and degenerative diseases, and is expected to return new knowledge in a as well, such as materials science.
But scientists needed time to run their experiments, Mr Dordain said.
The ISS project is a partnership of five - the US, Russia, Europe, Japan and Canada.
One of the biggest issues holding up an agreement on station-life extension is the human spaceflight review ordered by US President Barack Obama.
The Americans are developing a new vision for space exploration, and the rockets and spacecraft they will need to implement it. The future of US participation in the ISS is intimately tied to the outcome of the review.
Mr Dordain said no one partner in the ISS project could unilaterally call an end to the platform. A meeting would be held in Japan later in the year where he hoped the partners could get some clarity going forward.
"The decision must be taken early enough to put the budget in place, to build the hardware necessary and to decide on which transportation policy we shall use between 2015 and 2020. There are lot of aspects to be discussed and if decisions are not taken by the end of this year - beginning of next year - it will become more and more difficult to have the approach under which we will exploit the space station."
Mr Dordain said it was also essential the benefits were increased and the costs were reduced.
Increasing the benefits could include finding new uses for the station.
Esa has called for ideas on how to use the ISS as a platform for Earth observation. Mr Dordain said the agency had received about 20 very good proposals.
On the issue of reducing costs, there were many ideas on the table, he explained.
"First of all, we have four control centres - one in Houston, one in Oberpfaffenhofen, one in Moscow and one in Tsukuba - and these four control centres are working 24 hours a day. Question mark: Why can't we use only two of them for 12 hours and then the other two for 12 hours?"
He also questioned whether it was necessary for the station to be staffed by six astronauts at all times. If there were periods when little maintenance was required or the experiment load was light, could the ISS run on a smaller crew, he suggested.
One way to reduce costs would be to bring in new partners outside the current five - something Mr Dordain is keen to see discussed.
Construction of the space station is due to finish this year. Next month, two components built in Europe - a connecting node and a robotic control room - will be flown to the platform by the US shuttle Endeavour.
Tranquility and the Cupola, as they are known, will complete the non-Russian side of the ISS.
Some expected highlights for Europe in space in 2010:
FINISHING THE INTERNATIONAL SPACE STATION (ISS)
In early February, Europe's last major construction items for the space station head into orbit on the US shuttle Endeavour. is a connecting node that will house much of the life support equipment on the ISS. Attached to this module will be the Cupola, an observation room from where astronauts will direct robotic operations on the exterior of the station. Europe has now produced more than half of the pressurised volume on the US side of the orbiting platform.
A SECOND CHANCE FOR CRYOSAT
After the successful launches last year of its and Earth observation satellites, Esa will look to place in orbit. This spacecraft is a re-build of the mission in 2005. It will map the ice on the sea and on the land in the Arctic and the Antarctic. Goce, Smos and Cryosat-2 are part of the agency's Earth Explorer programme, which seeks swift answers to issues of pressing environmental concern.
Mars 500 - A SIMULATED MISSION TO THE RED PLANET
There is sure to be a lot of interest in the progress of this project, which will see an international crew of six make a 520-day round-trip to Mars. They will not actually leave Earth; they will be in a sealed facility in Moscow, Russia. The is to investigate the psychological and medical aspects of long-duration spaceflight. The crew are all volunteers. They will be split into two groups for a 30-day period when a "surface expedition" takes place.
A NEW BEGINNING FOR THE VENERABLE SOYUZ
The Russian Soyuz rocket is scheduled to make its maiden flight from French Guiana in July. Europe has helped construct for the vehicle at Sinnamary, just to the northwest of the established Kourou spaceport used by the Ariane 5. Soyuz will experience a 50% increase in performance merely by launching from an equatorial location. It will become a key player in the roll-out of Europe's .
EUROPEAN ASTRONAUTS PLAY LEADING ROLES
Esa's astronaut corps has enjoyed plenty of flight opportunities in recent years, culminating in being made commander of the space station in late 2009. Two Italians will fly the flag for Europe this year. Paolo Nespoli will undertake a long-duration tour on the ISS, while Roberto Vittori will be on the penultimate shuttle flight. Vittori's mission to the station will deliver a large physics experiment called the .
GALILEO - NEXT-GENERATION SAT-NAV
The first two for Galileo are scheduled to launch on a Soyuz rocket from Sinnamary in November. The IOVs (two more will follow in 2011) will prove Europe's satellite-navigation system works according to the design specification. The four pathfinders will then be joined in orbit by further satellites, starting in 2012. The intention is to have an operational Galileo - albeit a partial network - up and running by early 2014.
EUROPE'S SECOND SPACE TRUCK - JOHANNES KEPLER
The second Automated Transfer Vehicle (ATV) should fly towards the end of 2010. Named after will transport about six tonnes of air, water, food, fuel and equipment to the ISS astronauts. The freighter will also push the station higher into the sky to avoid the drag from residual air molecules at the top of the atmosphere. Without this type of re-boost effort, the station would eventually fall back to Earth.
VEGA - A NEW CLASS OF EUROPEAN ROCKET
The maiden flight of Vega from the Kourou spaceport could be an end-of-year highlight for Esa. This new rocket will be used for institutional payloads (300-2,000kg) such as the Earth Explorers that currently ride into orbit on ex-Soviet, converted ICBMs. Vega uses primarily solid propulsion and builds on the expertise developed for the side-mounted boosters of the Ariane 5. Vega's first "passengers" will include a French physics experiment to test aspects of Einstein's theory of general relativity.