Mr Cameron is to make a statement setting out how he will seek to form a government at 1430 BST. The Conservatives said he would spell out how he would try to form an administration which is "strong and stable with broad support, that acts in the national interest".
It follows Mr Clegg's comments that he believed the Tories had gained "first right" to attempt to form a government in the "national interest".
Speaking outside Lib Dem headquarters in London, Nick Clegg said: "It is vital that all parties, all political leaders, act in the national interest and not out of narrow party political advantage."
David Cameron is to set out within hours his plans to form a "stable" government, after the Tories won most votes but not an overall majority.
With results still coming in, the Tories have 292 seats in a hung parliament. He will say he plans to govern "in the national interest".
Nick Clegg, leader of the third biggest party the Lib Dems, said the Tories had the first right to seek to govern.
But Labour leader Gordon Brown is also hoping for a deal with the Lib Dems.
As counting continues the Tories have gained 92 seats, Labour have lost 87 and the Lib Dems five, despite hopes of a breakthrough for the third party.