Prime Minister Pedro Sanchez promised more coronavirus testing to try to build on a decline in daily Covid-19 deaths that has allowed Spain to start tentatively reopening its locked-down economy.
Officials hope more testing will give a better indication oft he areas where lock-downs can be eased further.
"Spain is already one of the countries making the most daily tests. More than 20,000, and we are increasing the number,"Sanchez told a near-empty parliament.
Spain's daily number of deaths from the coronavirus fell to 523 on Wednesday from 567 the day before, the health ministry said - well below a peak of 950 reached on 2 April.
The International Monetary Fund has said Spain's economy is likely to suffer heavily from the pandemic, and the government is keen to reactivate whatever businesses it can as soon as possible, especially ahead of the tourist summer months.
The IMF expected an 8% economic slump this year, because of the collapse in tourism and Spain's high proportion of small and medium-sized businesses, with the debt-to-GDP ratio projected to hit 113% - its highest level in over a century. It put the 2020 budget deficit at 9.5% of GDP, the widest in the euro zone.
On Monday and Tuesday, sectors including construction and manufacturing were allowed to reopen but, with most people still confined to their homes, shops, bars and public spaces will stay closed until at least April 26.
For the lockdown to be eased more broadly, officials say testing for the virus has to be expanded to include people who have mild or no symptoms, to track the spread in more detail.
The government also said last week it would carry out mass antibody tests on the blood of 60,000 randomly chosen people over three weeks, to begin identifying those who might in theory now be immune after exposure to the virus.
However, health and virology experts are not yet certain about the quality of such tests, or how much immunity such antibodies might provide.
Spain remains one of the world's worst-affected countries,with only the United States and Italy recording higher cumulative death tolls than the 18,579 reported on Wednesday.
The official tally of cases rose by just over 5,000 to 177,633, although Fernando Simon, the national emergency coordinator, said the expansion of testing had meant more mild or asymptomatic cases were being recorded.
