The Lithuanian Social Democratic Party (LSDP) will not sign the deal, because it does not back proposals to boost defense spending and make decisions on universal military conscription.
"As to the defense policy, (...) an agreement among parties will be signed on Monday," the speaker told reporters after the Seimas board's meeting with President Dalia Grybauskaitė.
The draft document, among other things, calls for gradually increasing defense spending to 2.5 percent of GDP by 2030 and for decisions on introducing universal military conscription to be made in 2022.
The LDSP does not approve of these two clauses and will not sign the agreement on Monday, Gintautas Paluckas, the party's leader, told BNS on Thursday.
The initiators of the new dealt say it would help ensure a consistent defense policy that will not be influenced by election cycles and changes in the political government.
The last time the country's political parties signed an agreement on defense and security policy was in 2014, shortly after the annexation of Crimea by Russia. Its key provision of increasing defense spending to 2 percent of GDP is set to be implemented this year.