The two senior Democrat and Republican Senators that Prime Minister John Key had been due to meet today pulled out because of the debt ceiling crisis.

Democrat Harry Reid and Republican Mitch McConnell are in the thick of negotiations with colleagues and President Barack Obama to raise the Government"s $14.3 trillion debt ceiling by August 2 to avoid running out of money.

Senator John Kerry, the chairman of the foreign relations committee and Republican Senator Richard Lugar stood in for them and greeted Mr Key who had been in meetings all morning.

Senate aides said the Senate would sit Sunday and possibly Saturday too to thrash out a deal to resolve the impasse.

The temperatures in Washington have soared to a sweltering 40 deg Celsius and later today Mr Key will leave his air conditioned meeting rooms to lay a wreath at Arlington military cemetery.

Chatting to reporters before Mr Key's arrival, Senator Kerry said he had visited New Zealand last year as a tourist on a camper van holiday with one of his stepsons and loved it, especially swimming with dolphins.

Senator Kerry is also due to take Mr Key onto the floor of the Senate later today to meet senior senators.

Mr Key met Treasury Secretary Timothy Geithner this morning and Homeland Security Secretary Janet Napolitano.

He began the day speaking to the American Chamber of Commerce where one of its senior vice-presidents, Myron Brilliant, urged Mr key to remind the key players on Capital Hill that the world was watching and that there was a lot at stake.

Mr Key said he hoped that at the Apec meeting in Honolulu in November, there would be momentum behind the Trans Pacific Partnership talks and that it was still "the best deal in town."

He called for more collaboration between New Zealand and the United States to help meet the demands of the growing middle class in Asia in the supply chain.