It follows fears over the future of the 1500 workers at the BAE Systems site after it emerged at the weekend the shipyard's five giant cranes are to be demolished.
Scotstoun is pinning its hopes on the Type 26 Frigates contract coming to the Clyde with a decision possibly due this month.
It is widely expected the workforce will be reduced, but there is no word whether that will be at Govan or at BAE's yard at Scotstoun, also on the Clyde, or both.
Any closure of Govan would have a big economic impact on the local area with many small businesses dependent on the yard's workers for their custom.
The GMB union's Jim Moohan and chairman of the Confederation of Shipbuilding and Engineering, said the UK Government must make an announcement to allow BAE to plan ahead and let staff know their future.
Mr Moohan said: "There has been speculation for some time now in relation to the long-term future of the shipyards.
"We are waiting for the Ministry of Defence [MoD] through BAE to confirm what the long-term strategy is.
" It does create a cloud of uncertainty and in the background we are aware big changes are afoot. But the MoD and the Government have to come clean very soon."
Previously workers at the yards have been laid off because of gaps in the order book despite it being known work is coming.
Mr Moohan said that needed to be avoided and continuity is crucial for workforce retention.
He said: "It is important the Type 26 order is placed to run parallel with current workload.
"The workers have been loyal and committed for the last 12 years and BAE has invested in infrastructure and skills in both Clyde yards. Whether it is for three or six ships we hope the announcement from the MoD is soon to allow BAE to plan."
Clydeport is removing the cranes at the request of BAE. It said the timing is not connected to the imminent decision to close one of its three yards, with Portsmouth also under threat.