With more than 80% of the votes of Sunday's legislative election counted, Alvaro Uribe appears to have strengthened his grip on Congress, setting the stage for passage of a US free-trade deal and a toughening of security policy.
The 53-year-old lawyer, a favourite of Washington and Wall Street for his market-friendly economic policies and crackdown on drug-running Marxist rebels, is expected to win a second four-year term in May.
He has had legislative support but struggled to form reliable majorities needed to drive through fiscal reforms.
German Espejo, an analyst with Security and Democracy, a think-tank in Bogota, said: "This is an endorsement of Uribe's security policies. So you can expect the government's stance against the guerrillas to toughen, at least until Uribe can drive them to the negotiating table.
"These results point to a clear re-election victory for Uribe in May."
However, turnout was less than half the 26.5 million registered voters.
Uribe's Party of the U won 20 seats in the 102-member Senate, followed by his allies the Conservatives, with 18 seats and Radical Change with 15.
The opposition Liberal Party, headed by Cesar Gaviria, a former president, won 17 Senate seats, while the other main opposition group, Democratic Pole, took 11.
Early results indicated similar gains for pro-Uribe parties in the lower house.
Juan Carlos Echeverry, head of economics at Bogota's University of the Andes, said the results indicated Congress would help Uribe cement Colombia's place as the main US ally in a region that has elected leaders Washington considers unfriendly, in recent elections.
"The parties that won today are committed to free trade and Uribe's economic reform agenda. This is good news from the market's point of view," Echeverry said.
Uribe is seen as a Washington
and Wall Street favourite
The trade pact signed by Washington and Colombia last month needs to be approved by legislators in both countries. Uribe wants Congress to help him shift the tax burden from companies to consumers to try to boost investment.
Talks with rebels
Uribe is popular in Colombia for cutting urban crime as part of his military campaign against the rebel Revolutionary Armed Forces of Colombia, or Farc.
And the president immediately used his renewed political strength to urge guerrillas to revive stalled peace talks.
"I ask the Revolutionary Armed Forces of Colombia to revise its behaviour, review the democratic calling of all Colombians and consider the possibility of serious and urgent peace talks," he said.
Farc, with 18,000 fighters, is the largest and best-equipped rebel force in Colombia. The rebels stepped up their attacks to defend their influence in rural areas ahead of the elections, killing dozens of mostly civilians but apparently failing to disrupt the vote.
Thousands die and tens of thousands are forced from their homes every year in Colombia's decades-old guerrilla war.