Mark V. Holden, left, senior vice president and general counsel for Koch Industries, chats with his boss Charles Koch in Wichita, Kansas, in 2015. (Nikki Kahn/The Washington Post)

INDIAN WELLS, Calif. — The Koch network plans to spend between $300 million to $400 million on policy and political campaigns during the 2018 election cycle.

Officials revealed the target budget at the start of a three-day donor summit at a resort here, indicating that they intend to continue expanding their reach at a time when Republicans control Congress and the White House. By comparison, the network spent about $250 million during the 2016 cycle on policy and political efforts.

The funds will be spread across a constellation of groups, including Americans for Prosperity and Freedom Partners Action Fund, along with Concerned Veterans for America, the Libre Initiative and Generation Opportunity, which now operate under the AFP banner.

Leaders from the groups said that they plan to focus on building up the capabilities of their grass-roots organization, which has boots on the ground in 36 states, and that the precise amount will depend on opportunities.

More than 550 donors are attending the seminar, the largest contingent ever. The network, which is led by billionaire industrialist Charles Koch, has about 700 donors who give a minimum of $100,000 per year. About 200 of the donors gathered at a desert resort outside of Palm Springs this weekend are first-time attendees. The seminar has happened twice annually since 2003.

In the last election cycle, the network put its political focus on backing a group of targeted Senate Republican candidates, declining to endorse a presidential candidate. That decision frustrated some donors, who urged Koch to back Donald Trump once he secured the GOP nomination. But the longtime libertarian patron refused, expressing dismay with Trump's comments about immigrants and Muslims.

No one from the Trump administration is attending this weekend's conclave. However, five Republican senators are on hand: Patrick J. Toomey (Pa.), David Perdue (Ga.), Ben Sasse (Neb.), Mike Lee (Utah) and James Lankford (Okla.). So are two House members, Jason Chaffetz (Utah) and Marsha Blackburn (Tenn.). And three governors flew in: Wisconsin’s Scott Walker, Arizona’s Doug Ducey and Illinois’s Bruce Rauner.

This post has been updated.