The Sri Lankan president's new allies say the ceasefire with Tamil Tiger rebels threatens national security.
The Tigers want autonomy for minority Tamils
A spokesman for the People's Liberation Front (JVP) said his party was ready to discuss a new truce agreement on the basis of "reasonable demands".
President Chandrika Kumaratunga has repeatedly stressed her commitment to upholding the two-year ceasefire.
She called April's poll after months of deadlock with her government, accusing it of being too soft on the Tigers.
JVP propaganda secretary Wimal Weerawansa told a weekly paper sympathetic to his party that his party had no intention of carrying the truce forward.
The BBC's Frances Harrison in Colombo says
the rebels are unlikely to be keen to start negotiations again from scratch, having spent months bargaining over the details of the ceasefire agreement with the last government.
If her alliance does win, it is not clear whether the president or her more hardline allies would decide policy.
The president's party announced a deal to contest the parliamentary elections in alliance with former leftist revolutionaries of the JVP three weeks ago.
JVP demo: The party opposes devolving power to the rebels
Mr Weerawansa, who was not available for comment, told the paper the truce agreement was clearly a threat to national security.
The Tigers have not rejected negotiations with the president's new alliance but they have expressed concern about its contradictory statements.
However, they are known to be wary and a recent rebel newspaper editorial did denounce the JVP as the Taleban of Sri Lanka.
Our correspondent says what worries the Tigers is that the JVP has in effect rejected a federal solution to the conflict and wants to review the role of the Norwegian mediators in the peace process.