Canada and Japan must open their markets to farm imports under a Pacific trade pact, the chairman of a U.S. congressional committee responsible for trade said on Thursday, adding that any country that cannot meet the deal's goals should drop out.

Negotiators from 12 Pacific countries hope to wrap up talks on the Trans-Pacific Partnership (TPP) within months, but House Ways and Means Committee Chairman Paul Ryan said some countries might have to wait for the second round.

"For TPP, Japan and Canada just have to lower their agricultural tariffs," he said at an event hosted by the Washington International Trade Association.

"Those have to go. And if any of the 12 countries currently in the talks think our standards are too high, well, I'd complete the agreement without them and invite them to join it later."

Ryan also said it was vital to pass legislation know as trade promotion authority (TPA) as soon as possible to streamline the passage of trade deals though Congress.

Japan is eager to protect sectors including beef, sugar and dairy, although Japanese media have reported the government is considering concessions.

Canada uses milk quotas and import tariffs to ensure steady prices for local farmers.

U.S. dairy farmers cheered Ryan's remarks. "Too many times in the past, Canada has gotten a pass on its impenetrable tariff wall on dairy imports," National Milk Producers Federation President Jim Mulhern said.

Canadian Agriculture Minister Gerry Ritz, speaking on a conference call with reporters during a visit to Washington, said he was confident Canada would remain in the TPP.

"There's a lot of pushing and shoving when you get to these steps in the negotiations. Everyone has defensive and offensive positions," he said, declining to comment on whether Canada would ease back on supply management.

Ritz, who has said it would take a "sea shift" for Canada to open its dairy, egg and poultry industries, noted the United States still had to re-enact TPA, which expired in 2007.

Under trade promotion authority, the executive branch negotiates, with Congress's input, trade agreements. Once an agreement has been negotiated, under TPA it is fast-tracked, meaning it cannot be amended by Congress and is subject to simple up or down votes in the House and Senate.

"At the end of the day of course everyone is looking at the ability of the American administration to push through with the TPA," he said.

A group of 70 food and agricultural organizations including Wal-Mart Stores on Thursday urged quick passage of TPA.